Led filament and led light bulb

ABSTRACT

An LED filament, comprising: an enclosure; a linear array of LED devices; and an electrical connector, wherein: the enclosure includes an optically transmissive binder; and the linear of LED devices is conformally wrapped around by the enclosure to be operable to emit light when energized through the electrical connector.

RELATED APPLICATIONS

The present application claims priority to CN201510502630.3 filed Aug.17, 2015, CN201510966906.3 filed Dec. 19, 2015, CN201610041667.5 filedJan. 22, 2016, CN201610281600.9 filed Apr. 29, 2016, CN201610272153.0filed Apr. 27, 2016, CN201610394610.3 filed Jun. 3, 2016,CN201610586388.7 filed Jul. 22, 2016, CN201610544049.2 filed Jul. 7,2016, CN201610936171.4 filed Nov. 1, 2016, CN201611108722.4 filed Dec.6, 2016, CN201710024877.8 filed Jan. 13, 2017, CN201710079423.0 filedFeb. 14, 2017, CN201710138009.2 filed Mar. 9, 2017, CN201710180574.5filed Mar. 23, 2017, CN201710234618.8 filed Apr. 11, 2017 andCN201710316641.1 filed May 8, 2017, each of which is incorporated hereinby reference in its entirety.

The present application is a continuation-in-part application of U.S.Ser. No. 15/384,311 filed Dec. 19, 2016, which claims priority toCN201510502630.3 filed Aug. 17, 2015, CN201510966906.3 filed Dec. 19,2015, CN201610041667.5 filed Jan. 22, 2016, CN201610281600.9 filed Apr.29, 2016, CN201610272153.0 filed Apr. 27, 2016, CN201610394610.3 filedJun. 3, 2016, CN201610586388.7 filed Jul. 22, 2016, CN201610544049.2filed Jul. 7, 2016, CN201610936171.4 filed Nov. 1, 2016 andCN201611108722.4 filed Dec. 6, 2016, and which is a continuation-in-partapplication of U.S. Ser. No. 15/366,535 filed Dec. 1, 2016, which claimspriority to CN201510502630.3 filed Aug. 17, 2015, CN201510966906.3 filedDec. 19, 2015, CN201610041667.5 filed Jan. 22, 2016, CN201610281600.9filed Apr. 29, 2016, CN201610272153.0 filed Apr. 27, 2016,CN201610394610.3 filed Jun. 3, 2016, CN201610586388.7 filed Jul. 22,2016, CN201610544049.2 filed Jul. 7, 2016 and CN201610936171.4 filedNov. 1, 2016, and which is a continuation-in-part application of U.S.Ser. No. 15/237,983 filed Aug. 16, 2016, which claims priority toCN201510502630.3 filed Aug. 17, 2015, CN201510966906.3 filed Dec. 19,2015, CN201610041667.5 filed Jan. 22, 2016, CN201610272153.0 filed Apr.27, 2016, CN201610281600.9 filed Apr. 29, 2016, CN201610394610.3 filedJun. 3, 2016 and CN201610586388.7 filed Jul. 22, 2016, each of which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to LED luminaries. More particularly, thisinvention describes an LED filament and an LED light bulb.

BACKGROUND OF THE INVENTION

Incandescent light bulbs are a source of electric light that createslight by running electricity through a resistive filament, therebyheating the filament to a very high temperature, so that it glows andproduces visible light. Incandescent bulbs are made in a wide range ofsizes and voltages, from 1.5 volts to about 300 volts. The bulbs consistof a generally glass or plastic enclosure with a filament of tungstenwire inside the bulb through which an electrical current is passed.Incandescent lamps are designed as direct “plug-in” components that matewith a lampholder via a threaded Edison base connector (sometimesreferred to as an “Edison base” in the context of an incandescent lightbulb), a bayonet-type base connector (i.e., bayonet base in the case ofan incandescent light bulb), or other standard base connector to receivestandard electrical power (e.g., 120 volts A.C., 60 Hz in the UnitedStates, or 230V A.C., 50 Hz in Europe, or 12 or 24 or other D.C.voltage). The base provides electrical connections to the filament.Usually a stem or glass mount anchors to the base, allowing theelectrical contacts to run through the envelope without gas or airleaks.

Incandescent light bulbs are widely used in household and commerciallighting, for portable lighting, such as table lamps, car headlamps,flashlights, and for decorative and advertising lighting. However,incandescent light bulbs are generally inefficient in terms of energyuse and are subject to frequent replacement due to their limitedlifetime (about 1,000 hours). Approximately 90% of the energy input isemitted as heat. These lamps are gradually being replaced by other, moreefficient types of electric light such as fluorescent lamps,high-intensity discharge lamps, light emitting diodes (LEDs), etc. Forthe same energy input, these technologies give more visible light andgenerate much less heat. Particularly, LEDs consume a fraction of theenergy used to illuminate incandescent bulbs and have a much longerlifetime (e.g. 50,000 to 75,000 hours). Furthermore, LED light sourcesare a very clean “green” light source and also provide good colorreproduction.

LED light bulbs are far more efficient than traditional incandescentlamps, most notably because they use only a small fraction of theelectricity of an incandescent. As traditional incandescent bulbscontinue to be phased out, LED has become the mainstream light sourcesused on a variety of indoor and outdoor lighting fixtures. However,traditional LED light bulbs are not without its disadvantages, forexample, the complicated designs which incorporate the heavy aluminumheat sinks and an electronic circuit for power conversion. Consequently,the cost is high and the shape is somewhat strange compared with theelegant incandescent bulbs people are accustomed to.

An LED filament bulb is a light bulb that uses LEDs as its filaments.Accordingly, it is desirable to provide a novel LED filament light bulbwith improved performance and aesthetics that may be used as a betterreplacement for a typical incandescent light bulb than traditional LEDlight bulbs.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention that light is emitted from oneor more LED filaments uniformly and evenly in all directions, instead ofbeaming in a direction while leaving everywhere else dark the way thatmany traditional LED light bulbs do. Thus, the LED filament light bulbfeatures a close resemblance with the traditional incandescent bulb.Desirably, the visually unpleasant aluminum die cast for heatdissipation in traditional LED light bulbs is no longer required in theLED filament light bulb. Thus, the LED filament light bulb is perfectfor homes, hotels, restaurants, bars and places where classic style andappearance is critical. Desirably, all electronics of the LED filamentlight bulb is nestled inside the light bulb which is almost not visible.Desirably, light produced by the LED filament light bulb is similar tonatural light. It does not have any infrared or ultraviolet radiationand it is uniform and soft on the eyes. After the regulations thatbanned the sale of the traditional light bulbs, many homeowners couldnot put in compact fluorescent bulbs or other bogus LED lights into mostof these old fixtures and chandeliers. Desirably, the LED filament lightbulb fits well into all the lighting fixtures that used the outdatedincandescent light bulbs. Desirably, the LED filament light bulb makesit easy to reuse these old and attractive lighting fixtures. Desirably,the LED filament light bulb have remarkable energy efficiency.Desirably, the LED filament has a long service life. This extendedlifespan is enhanced by a constant current source that ensures stabilityof parameters and prolongs the life of the light bulb. Hence, the costof investing in these bulbs will provide cost savings for up to a fewdecades in some cases. Desirably, the LED filament light bulb can beplaced in places where dimming of lights is necessary. The LED filamentlight bulb gives off a warm inviting golden soft glow when used in tablelamps or as accent lights. The LED filament light bulb is perfect forcreating a very pleasant atmosphere in sitting rooms or bedrooms.

Therefore, it is an object of the claimed invention to provide asignificantly improved LED filament for using with an LED light bulb. Inaccordance with an embodiment with the present invention, the LEDfilament comprises an enclosure; a linear array of LED devices; and anelectrical connector, wherein: the enclosure includes an opticallytransmissive binder; and the linear of LED devices is conformallywrapped around by the enclosure to be operable to emit light whenenergized through the electrical connector.

In accordance with an embodiment with the present invention, LEDfilament is capable of self-sustained plastic deformation formaintaining a suitable posture in an LED light bulb.

In accordance with an embodiment with the present invention, the LEDfilament maintains the suitable posture in the LED light bulb byphysically attaching the electrical connector to a lead wire of the LEDlight bulb.

In accordance with an embodiment with the present invention, theenclosure includes a posture maintainer.

In accordance with an embodiment with the present invention, the posturemaintainer includes a pre-determined concentration of particles harderthan the optically transmissive binder in which the particles areembedded.

In accordance with an embodiment with the present invention, the posturemaintainer includes a pre-determined concentration of phosphorparticles.

In accordance with an embodiment with the present invention, theenclosure includes alternate coatings of the optically transmissivebinder and the phosphor particles.

In accordance with an embodiment with the present invention, the posturemaintainer includes a wire system embedded in the optically transmissivebinder.

In accordance with an embodiment with the present invention, the posturemaintainer includes an aperture system beneath a surface of theenclosure where tight turns are planned for the posture the LED filamentis designed to maintain in the LED light bulb.

In accordance with an embodiment with the present invention, theenclosure is fabricated and tested independently of the linear array ofLED devices; and the enclosure is adhesively bonded to the linear arrayof LED devices to form the LED filament in a unitary structure.

In accordance with an embodiment with the present invention, theenclosure has a texturized outer surface for improving light extraction.

In accordance with an embodiment with the present invention, theenclosure has a texturized inner surface for improving light extraction.

In accordance with an embodiment with the present invention, wherein theLED device has a texturized light emission surface for improving lightextraction.

In accordance with an embodiment with the present invention, the LED diein the LED device has an elongated top view approximating a hypotheticalrectangle having a longitudinal axis substantially parallel to alongitudinal axis of the linear array of LED devices.

In accordance with an embodiment with the present invention, the aspectratio of the hypothetical rectangle is from 2:1 to 10:1.

In accordance with an embodiment with the present invention, the LEDdevices are interconnected with a bond wire; and a sinuosity of the bondwire is from 2 to 8.

In accordance with an embodiment with the present invention, the LEDdevices are interconnected with a glue wire; and the sinuosity of theglue wire is from 3 to 8.

In accordance with an embodiment with the present invention, the LEDdevices are interconnected with a flexible printed circuit film having aplurality of conductive tracks; and the ratio of a total area covered bythe plurality of conductive tracks to an area of the flexible printedcircuit film is from 0.1% to 20%.

In accordance with an embodiment with the present invention, theenclosure further includes a wavelength converter; the wavelengthconverter is formed by embedding a plurality of light conversionparticles in the optically transmissive binder; and the plurality oflight conversion particles is in a state of optimal conversion.

In accordance with an embodiment with the present invention, theenclosure further includes a wavelength converter; the wavelengthconverter is formed by embedding a plurality of light conversionparticles in the optically transmissive binder; and the plurality oflight conversion particles is in a state of thermal optimum for forminga plurality of heat transfer paths.

In accordance with an embodiment with the present invention, theplurality of heat transfer paths radiates like spokes of a wheel fromthe LED device like a hub of the wheel.

In accordance with an embodiment with the present invention, the ratioof a volume of the light conversion particles in the wavelengthconverter to a volume of the optically transmissive transparent binderin the wavelength converter is from 20:80 to 99:1.

In accordance with an embodiment with the present invention, the ratioof a weight of the light conversion particles in the wavelengthconverter to a weight of the optically transmissive binder in thewavelength converter is from 20% to 50%.

In accordance with an embodiment with the present invention, the LEDfilament, comprises an enclosure; a linear array of LED devices; and anelectrical connector, wherein the entire enclosure is a monolithicstructure made from a single piece of optically transmissive material.

In accordance with an embodiment with the present invention, theenclosure includes a first region and a second region having a differentset of properties from that of the first region.

In accordance with an embodiment with the present invention, the regionsof the enclosure are defined by a hypothetical plane perpendicular to alight illuminating direction of the linear array of LED devices.

In accordance with an embodiment with the present invention, theenclosure includes three regions defined by a pair of the hypotheticalplanes compartmentalizing the enclosure into an upper region, a lowerregion and a middle region sandwiched by the upper region and the lowerregion; the linear array of LED devices is disposed in the middleregion; a cross section perpendicular to a longitudinal axis of the LEDfilament reveals the middle region and other regions of the enclosure;R1 is a ratio of an area of the middle region to an overall area of thecross section; and R1 is from 0.2 to 0.8.

In accordance with an embodiment with the present invention, the regionsof the enclosure are defined by a hypothetical plane parallel to a lightilluminating direction of the linear array of LED devices.

In accordance with an embodiment with the present invention, theenclosure includes three regions defined by a pair of the hypotheticalplanes compartmentalizing the enclosure into a right region, a leftregion and a middle region sandwiched by the right region and the leftregion; the linear array of LED devices is disposed in the middleregion; a cross section perpendicular to a longitudinal axis of the LEDfilament reveals the middle region and other regions of the enclosure;R2 is a ratio of an area of the middle region to an overall area of thecross section; and R2 is from 0.2 to 0.8.

In accordance with an embodiment with the present invention, the regionsof the enclosure are defined by a hypothetical cylindrical surfacehaving a central axis of the LED filament as its central axis.

In accordance with an embodiment with the present invention, theenclosure includes three regions defined by a coaxial pair of thehypothetical cylindrical surfaces compartmentalizing the enclosure intoa core region, an outer region and a middle region sandwiched by thecore region and the outer region; and the linear array of LED devices isdisposed in the core region.

In accordance with an embodiment with the present invention, the crosssection perpendicular to a longitudinal axis of the LED filament revealsthe core region and other regions of the enclosure; R3 is a ratio of anarea of the core region to an overall area of the cross section; and R3is from 0.1 to 0.8.

In accordance with an embodiment with the present invention, the crosssection perpendicular to a longitudinal axis of the LED filament revealsthe middle region and other regions of the enclosure; R4 is a ratio ofan area of the middle region to an overall area of the cross section;and R4 is from 0.1 to 0.8.

In accordance with an embodiment with the present invention, the regionsof the enclosure are defined by a hypothetical set of parallel planesintersecting the enclosure perpendicularly to a longitudinal axis of theenclosure.

In accordance with an embodiment with the present invention, theenclosure includes two alternating regions including a first region anda second region defined by the hypothetical set of parallel planes; theLED device is disposed in the first region; a means for electricallyconnecting the LED devices is disposed in the second region; an outersurface of the enclosure shows a combination of the first region andother regions; R5 is a ratio of a total area of the first region foundon an outer surface of the enclosure to an overall area of the outersurface of the enclosure; and R5 is from 0.2 to 0.8.

In accordance with an embodiment with the present invention, the LEDfilament comprises an enclosure; a linear array of LED devices; and anelectrical connector, wherein the enclosure is a modular structureassembled from modules.

In accordance with an embodiment with the present invention, theenclosure includes a first module and a second module having a differentset of properties from that of the first module.

In accordance with an embodiment with the present invention, the modulesof the enclosure are defined by a hypothetical plane perpendicular to alight illuminating direction of the linear array of LED devices.

In accordance with an embodiment with the present invention, theenclosure includes three modules defined by a pair of the hypotheticalplanes compartmentalizing the enclosure into an upper module, a lowermodule and a middle module sandwiched by the upper module and the lowermodule; the linear array of LED devices is disposed in the middlemodule; a cross section perpendicular to a longitudinal axis of the LEDfilament reveals the middle module and other modules of the enclosure;R6 is a ratio of an area of the middle module to an overall area of thecross section; and R6 is from 0.2 to 0.8.

In accordance with an embodiment with the present invention, the modulesof the enclosure are defined by a hypothetical plane parallel to a lightilluminating direction of the linear array of LED devices.

In accordance with an embodiment with the present invention, theenclosure includes three modules defined by a pair of the hypotheticalplanes compartmentalizing the enclosure into a right module, a leftmodule and a middle module sandwiched by the right module and the leftmodule; the linear array of LED devices is disposed in the middlemodule; a cross section perpendicular to a longitudinal axis of the LEDfilament reveals the middle module and other modules of the enclosure;R7 is a ratio of an area of the middle module to an overall area of thecross section; and R7 is from 0.2 to 0.8.

In accordance with an embodiment with the present invention, the modulesof the enclosure are defined by a hypothetical cylindrical surfacehaving a central axis of the LED filament as a central axis of thehypothetical cylindrical surface.

In accordance with an embodiment with the present invention, theenclosure includes three modules defined by a coaxial pair of thehypothetical cylindrical surfaces compartmentalizing the enclosure intoa core module, an outer module and a middle module sandwiched by thecore module and the outer module; and the linear array of LED devices isdisposed in the core module.

In accordance with an embodiment with the present invention, the crosssection perpendicular to a longitudinal axis of the LED filament revealsthe core module and other modules of the enclosure; R8 is a ratio of anarea of the core module to an overall area of the cross section; and R8is from 0.1 to 0.8.

In accordance with an embodiment with the present invention, the crosssection perpendicular to a longitudinal axis of the LED filament revealsthe middle module and other modules of the enclosure; R9 is a ratio ofan area of the middle module to an overall area of the cross section;and R9 is from 0.1 to 0.8.

In accordance with an embodiment with the present invention, the modulesof the enclosure are defined by a hypothetical set of parallel planesintersecting the enclosure perpendicularly to a longitudinal axis of theenclosure.

In accordance with an embodiment with the present invention, theenclosure includes two alternating modules including a first module anda second module defined by the hypothetical set of parallel planes; theLED device is disposed in the first module; a means for electricallyconnecting the LED devices is disposed in the second module; an outersurface of the enclosure shows a combination of the first module andother modules; R10 is a ratio of a total area of the first module foundon an outer surface of the enclosure to an overall area of the outersurface of the enclosure; and R10 is from 0.2 to 0.8.

In accordance with an embodiment with the present invention, the LEDlight bulb comprises a base; light transmissive envelope; a stem press;an LED filament; and a plurality of lead wires, wherein: at least partof the base is metal for receiving electrical power; the lighttransmissive envelope is mounted on the base; the stem press is mountedon the base within the light transmissive envelope for holding the leadwire and the LED filament in position; the lead wire electricallycouples the base and the LED filament; the LED filament comprises anenclosure, a linear array of LED devices and an electrical connector;the enclosure includes an optically transmissive binder; the linear ofLED devices is conformally wrapped around by the enclosure to beoperable to emit light when energized through the electric connector;and a Cartesian coordinate system having an x-axis, a y-axis and az-axis is oriented for the LED light bulb where: (1) an interfaceconnecting the light transmissive envelope and base falls on the x-yplane; and (2) the z-axis, which is also a longitudinal axis of the LEDlight bulb, intersects the interface at point O.

In accordance with an embodiment with the present invention, the LEDfilament defines an arc extending substantially vertically in the lighttransmissive envelope; an endpoint of the arc reaches as high as pointH1 on the z-axis; the distance on the y-axis between the endpoints ofthe LED filament is D; the length of the LED filament on the z-axis isA1; the posture of the LED filament in the LED light bulb is defined byall points in a set (0, Y, Z+H1), where Z goes up from 0 to A1 and thenfrom A1 back to 0 as Y goes from −D/2 to 0 and then from 0 to D/2; M isa ratio of a length of the LED filament on the x-axis to a length of thelight transmissive envelope on the x-axis; N is a ratio of a length ofthe LED filament on the y-axis to a length of the light transmissiveenvelope on the y-axis; P is a ratio of a length of the LED filament onthe z-axis to a length of the light transmissive envelope on the z-axis;M is from 0 to 0.05; N is from 0.1 to 0.8; and P is from 0.1 to 0.8.

In accordance with an embodiment with the present invention, the LEDlight bulb further comprises a plurality of support wires, wherein: thestem press includes a basal portion for attaching the stem press to thebase and an elongated post portion for elevating the LED filament to adesired position in the light transmissive envelope; the plurality ofsupport wires radiates horizontally from the post portion to form aspoke-and-hub structure in the light transmissive envelope; the supportwire is attached to the post portion at a first end and to the LEDfilament at a second end; the LED filament defines a sinuous curve alongan arc meandering in the light transmissive envelope; the sinuous curvedefined by the LED filament oscillates in a range from H2+A2 to H2−A2 onthe z-axis, where H2 represents an average height of the LED filamentalong the z-axis in the LED light bulb and A2 represents an amplitude ofthe sinuous curve the LED filament defines; the plurality of supportwires has a same length R; the posture of the LED filament in the LEDlight bulb is defined by all points in a set (X, Y, Z+H2), where−R=<X=<R; −R=<Y=<R; and −A2=<Z=<A2; M is a ratio of a length of the LEDfilament on the x-axis to a length of the light transmissive envelope onthe x-axis; N is a ratio of a length of the LED filament on the y-axisto a length of the light transmissive envelope on the y-axis; P is aratio of a length of the LED filament on the z-axis to a length of thelight transmissive envelope on the z-axis; P is from 0.2 to 0.7; M isfrom 0.2 to 0.8; and N is from 0.2 to 0.8.

In accordance with an embodiment with the present invention, the LEDlight bulb further comprises an upper LED filament; a lower LEDfilament; an upper set of support wires; and a lower set of supportwires, wherein: the stem press includes a basal portion for attachingthe stem press to the base and an elongated post portion for elevatingthe LED filament to a desired position in the light transmissiveenvelope; the support wire radiates from the post portion to form aspoke-and-hub structure in the light transmissive envelope; the supportwire is attached to the post portion at a first end and to the LEDfilament at a second end; the upper set of support wires is configuredto hold the upper LED filament in position; the lower set of supportwires is configured to hold the lower LED filament in position; theupper LED filament defines an upper sinuous curve oscillating in a rangefrom H4+A4 to H4−A4 on the z-axis, where H4 represents an average heightof the upper LED filament in the LED light bulb and A4 represents anamplitude of the upper sinuous curve the upper LED filament defines; thelower LED filament defines a lower sinuous curve oscillating in a rangefrom H5+A5 to H5−A5 on the z-axis, where H5 represents an average heightof the lower LED filament in the LED light bulb and A5 represents anamplitude of the lower sinuous curve the lower LED filament defines; H5is less than H4; the plurality of support wires have a same length R;the posture of the upper LED filament in the LED light bulb is definedby all points in a set (X, Y, Z+H4), where −R=<X=<R; −R=<Y=<R; and−A4=<Z=<A4; the posture of the lower LED filament in the LED light bulbis defined by all points in a set (X, Y, Z+H5), where −R=<X=<R;−R=<Y=<R; and −A5=<Z=<A5; M is a ratio of an aggregate of lengths of thepair of LED filaments on the x-axis to a length of the lighttransmissive envelope on the x-axis; N is a ratio of an aggregate oflengths of the pair of LED filaments on the y-axis to a length of thelight transmissive envelope on the y-axis; P is a ratio of an aggregateof lengths of the pair of the LED filaments on the z-axis to a length ofthe light transmissive envelope on the z-axis; P is from 0.4 to 1.7; Mis from 0.4 to 1.6; and N is from 0.4 to 1.6.

In accordance with an embodiment with the present invention, the coreregion has greater thermal conductivity than the middle region, theouter region or both by doping in the core region a greaterconcentration of particles which are electrical insulators while havinggreater heat conductivity than phosphor particles; and the outer regionhas greater thermal radiation power than the middle region, the coreregion or both by doping in the outer region a greater concentration ofparticles having greater thermal radiation power than the opticallytransmissive binder and greater thermal conductivity than phosphorparticles.

Various other objects, advantages and features of the present inventionwill become readily apparent from the ensuing detailed description, andthe novel features will be particularly pointed out in the appendedclaims.

BRIEF DESCRIPTION OF FIGURES

The following detailed descriptions, given by way of example, and notintended to limit the present invention solely thereto, will be best beunderstood in conjunction with the accompanying figures:

FIG. 1 is a see-through view of the LED filament in accordance with anexemplary embodiment of the present invention;

FIG. 2 is a see-through view of the LED filament in accordance with anexemplary 1 embodiment of the present invention;

FIG. 3 is a see-through view of the LED filament in accordance with anexemplary embodiment of the present invention;

FIG. 4 is a cut-open view of the LED filament in accordance with anexemplary embodiment of the present invention;

FIGS. 5A to 5D are schematic views of the truncated LED filament inaccordance with an exemplary embodiment of the present invention;

FIGS. 6A to 6H are schematic views of the LED device in accordance withan exemplary embodiment of the present invention;

FIGS. 7A to 7D are schematic views of the linear array of LED devices inaccordance with an exemplary embodiment of the present invention;

FIGS. 8A to 8F are schematic views of the linear array of LED devices inaccordance with an exemplary embodiment of the present invention;

FIGS. 9A and 9B are schematic views of the LED filament in accordancewith an exemplary embodiment of the present invention;

FIGS. 10A to 10C are schematic views of the LED filament in accordancewith an exemplary embodiment of the present invention;

FIGS. 11A to 11C are schematic views of the LED filament in accordancewith an exemplary embodiment of the present invention;

FIGS. 12A to 12D are schematic views of the LED filament in accordancewith an exemplary embodiment of the present invention;

FIG. 13 is a see-through view of the LED filament in accordance with anexemplary embodiment of the present invention;

FIG. 14 shows the truncated LED filament in FIG. 13 in accordance withan exemplary embodiment of the present invention;

FIG. 15 shows a cutaway from the LED filament in FIG. 13 in accordancewith an exemplary embodiment of the present invention;

FIG. 16 shows a cutaway from the LED filament in FIG. 13 in accordancewith an exemplary embodiment of the present invention;

FIG. 17 shows a cutaway from the LED filament in FIG. 13 in accordancewith an exemplary embodiment of the present invention;

FIG. 18 shows a radial section of the truncated LED filament inaccordance with an exemplary embodiment of the present invention;

FIGS. 19A to 19C show a cross section of the LED filament in accordancewith an exemplary embodiment of the present invention;

FIGS. 20A to 20E show a truncated LED filament in accordance with anexemplary embodiment of the present invention;

FIGS. 20F and 20G show schematic views of the LED filament when it isstraight and when it is bent in accordance with an exemplary embodimentof the present invention;

FIGS. 21A to 21C show a cross section of the LED filament in accordancewith an exemplary embodiment of the present invention;

FIG. 22 shows a cutaway from the LED filament in FIG. 13 in accordancewith an exemplary embodiment of the present invention;

FIG. 23 shows a truncated LED filament cut into halves in accordancewith an exemplary embodiment of the present invention;

FIG. 24 shows a truncated LED filament cut into halves in accordancewith an exemplary embodiment of the present invention;

FIG. 25 shows a truncated LED filament carved into two portions inaccordance with an exemplary embodiment of the present invention;

FIG. 26 shows a truncated LED filament carved into two portions inaccordance with an exemplary embodiment of the present invention;

FIG. 27 shows a truncated LED filament carved into two portions inaccordance with an exemplary embodiment of the present invention;

FIG. 28 shows a truncated LED filament carved into two portions inaccordance with an exemplary embodiment of the present invention;

FIG. 30 shows a truncated LED filament assembled from two modules inaccordance with an exemplary embodiment of the present invention;

FIG. 31 shows a truncated LED filament assembled from two modules inaccordance with an exemplary embodiment of the present invention;

FIG. 32 shows a truncated LED filament assembled from two modules inaccordance with an exemplary embodiment of the present invention;

FIG. 33 shows an LED light bulb in accordance with an exemplaryembodiment of the present invention;

FIG. 34 shows an LED light bulb in accordance with an exemplaryembodiment of the present invention;

FIG. 35 shows an LED light bulb in accordance with an exemplaryembodiment of the present invention;

FIG. 36 shows an LED light bulb in accordance with an exemplaryembodiment of the present invention; and

FIG. 37 shows an LED light bulb in accordance with an exemplaryembodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention will be described more fully hereinafter with reference tothe accompanying drawings, in which example embodiments of the inventionare shown. This invention may, however, be embodied in many differentforms and should not be construed as limited to the example embodimentsset forth herein. Rather, the disclosed embodiments are provided so thatthis disclosure will be thorough and complete, and will fully convey thescope of the invention to those skilled in the art. In the drawings, thesize and relative sizes of layers and regions may be exaggerated forclarity. Like numbers refer to like elements throughout.

It will be understood that when an element or layer is referred to asbeing “on,” “connected to,” “coupled to” or “responsive to” (and/orvariants thereof) another element, it can be directly on or directlyconnected, coupled or responsive to the other element or interveningelements may be present. In contrast, when an element is referred to asbeing “directly on,” “directly connected to,” “directly coupled to” or“directly responsive to” (and/or variants thereof) another element,there are no intervening elements present. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items and may be abbreviated as “/”.

It will be understood that, although the terms first, second, third,etc. may be used herein to describe various elements, components,regions, layers and/or sections, these elements, components, regions,layers and/or sections should not be limited by these terms. These termsare only used to distinguish one element, component, region, layer orsection from another region, layer or section. Thus, a first element,component, region, layer or section discussed below could be termed asecond element, component, region, layer or section without departingfrom the teachings of the present invention.

The terminology used herein is for purposes of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising” (and/or variants thereof), when used in thisspecification, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof. In contrast,the term “consisting of ” (and/or variants thereof) when used in thisspecification, specifies the stated number of features, integers, steps,operations, elements, and/or components, and precludes additionalfeatures, integers, steps, operations, elements, and/or components.

The present invention is described below with reference to blockdiagrams and/or flowchart illustrations of methods and/or apparatus(systems) according to embodiments of the invention. It is understoodthat a block of the block diagrams and/or flowchart illustrations, andcombinations of blocks in the block diagrams and/or flowchartillustrations, can embody apparatus/systems (structure), means(function) and/or steps (methods) for implementing the functions/actsspecified in the block diagrams and/or flowchart block or blocks. Itshould also be noted that in some alternate implementations, thefunctions/acts noted in the blocks may occur out of the order noted inthe flowcharts. For example, two blocks shown in succession may in factbe executed substantially concurrently or the blocks may sometimes beexecuted in the reverse order, depending upon the functionality/actsinvolved. Moreover, the functionality of a given block of the flowchartsand/or block diagrams may be separated into multiple blocks and/or thefunctionality of two or more blocks of the flowcharts and/or blockdiagrams may be at least partially integrated.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or“top,” may be used herein to describe one element's relationship toanother element as illustrated in the Figures. It will be understoodthat relative terms are intended to encompass different orientations ofthe device in addition to the orientation depicted in the Figures. Forexample, if the device in one of the figures is turned over, elementsdescribed as being on the “lower” side of other elements would then beoriented on “upper” sides of the other elements. The exemplary term“lower”, can therefore, encompasses both an orientation of “lower” and“upper,” depending of the particular orientation of the figure.Similarly, if the device in one of the figures is turned over, elementsdescribed as “below” or “beneath” other elements would then be oriented“above” the other elements. The exemplary terms “below” or “beneath”can, therefore, encompass both an orientation of above and below.

Example embodiments of the invention are described herein with referenceto cross-section illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of the invention. Assuch, variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, may be expected.Thus, the disclosed example embodiments of the invention should not beconstrued as limited to the particular shapes of regions illustratedherein unless expressly so defined herein, but are to include deviationsin shapes that result, for example, from manufacturing. For example, animplanted region illustrated as a rectangle will, typically, haverounded or curved features and/or a gradient of implant concentration atits edges rather than a binary change from implanted to non-implantedregion. Likewise, a buried region formed by implantation may result insome implantation in the region between the buried region and thesurface through which the implantation takes place. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the actual shape of a region of a device andare not intended to limit the scope of the invention, unless expresslyso defined herein.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which the present invention belongs. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent application, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein. Documentsincorporated by reference are meant to provide contexts for and shouldby no means be construed to contradict the disclosure in the presentapplication. Particularly, the following terms are deemedinterchangeable unless otherwise expressly distinguished: (1) lightconversion coating and (2) enclosure. Unless otherwise expresslydefined, a filament body includes a light conversion coating (i.e. anenclosure) and a plurality of LED devices.

FIG. 1 is a see-through view of the LED filament 100 in accordance withan exemplary embodiment of the present invention. The LED filament 100includes an enclosure 108, a linear array of LED devices 102 and anelectrical connector 506. The linear array of LED devices 102 isdisposed in the enclosure 108 to be operable to emit light whenenergized through the electrical connector 506. The enclosure 108 is anelongated structure preferably made of primarily flexible materials suchas silicone. The enclosure 108 has either a fixed shape or, if made of aflexible material, a variable shape. The enclosure 108 is thus capableof maintaining either a straight posture or curvaceous posture (e.g.like a gift ribbon or helical spiral), with or without external supportdepending on applications, in an LED light bulb. The enclosure 108 has across section in any regular shapes (e.g. circle and polygon) or anyirregular shapes (e.g. petal and star). The enclosure 108 includes ahollow space longitudinally extending inside the enclosure 108 forhousing the linear array of LED devices 102 and the electrical connector506. In an embodiment, exactly one LED filament—instead of an array ofLED filaments assembled from a plurality of LED filaments in someembodiments—is used for generating omnidirectional light in an LED lightbulb because the LED filament is configured to maintain a suitable aposture in the light bulb. The cost and reliability of an LED lightbulb, when only one LED filament is used, will be improved becausepotential issues such as weak soldering points are reduced. In FIG. 1,the enclosure 108 is a straight cylinder having a circular crosssection. The enclosure 108 is made of any optically transmissivematerials through which optical radiation from the LED device 102 canpass without being totally absorbed or reflected, e.g. glass, plastic,resin and silicone. The linear array of LED devices 102 includes aplurality of LED devices 102 electrically coupled in parallel, in seriesor in a combination of both ways. In FIGS. 1 and 2, the linear array ofLED devices 102 is formed by serially coupling a plurality of LEDdevices 102. In FIG. 1, the linear array of LED devices 102 defines astraight line in the enclosure 108 along the longitudinal axis of theenclosure 108. In FIG. 2, the linear array of LED devices 102 defines aU-shaped curve extending axially in the enclosure 108. In FIG. 3, thelinear array of LED devise 1021, 1022 includes a first set of seriallycoupled LED devices 1021 and a second set of serially coupled LEDdevices 1022. The first set of LED devices 1021 is in parallelconnection with the second set of LED devices 1022. The linear array ofLED devices 1021, 1022 defines a straight pair of parallel linesextending axially in the enclosure 108. Because there is only one pathin which the current can flow in a series circuit, opening or breakingthe circuit at any point causes the entire array of LED devices 1021,1022 in the series to stop operating. By contrast, the same voltage isapplicable to all components connected in parallel. The total current isthe sum of the currents through individual components. Other thingsequal including luminary output, lower current in an individual LEDdevice 102 results in better thermal performance.

The linear array of LED devices 102 includes a liner array of single-diedevices, multi-die devices or both to enable the LED filament to glowacross a broad field of angle. Going back to FIG. 1, in someembodiments, the linear array of LED devices 102 includes a plurality ofindividual LED dies connected by conductive glue, solder or welds. LEDdevices 102 having different colors can be mixed together to createwhite light. In other embodiments, the linear array of LED devices 102includes a plurality of multi-die LED devices coupled together by a wireframe structure or in some other manner. The linear array of LED devices102 emits light in a substantially omnidirectional or 360-degree patternfrom the LED filament 100. Light is given off around the enclosure 108roughly perpendicular to the envelope of the enclosure 108 in alldirections. While the desired light intensity distribution may compriseany light intensity distribution, in one embodiment, the desired lightintensity distribution conforms to the JEL801 standards or ENERGY STAR®Partnership Agreement Requirements for Luminous Intensity Distribution,each of which is incorporated herein by reference. Under ENERGY STAR®standards, an omnidirectional lamp is one configured to emit “an evendistribution of luminous intensity (candelas) within the 0° to 135° zone(vertically axially symmetrical). Luminous intensity at any angle withinthis zone shall not differ from the mean luminous intensity for theentire 0° to 135° zone by more than 20%. At least 5% of total flux(lumens) must be emitted in the 135° to 180° zone. Distribution shall bevertically symmetrical as measures in three vertical planes at 0°, 45°and 90°.” The Japanese standard JEL801 stipulates that the luminary fluxwithin 120 degrees from the beaming axis must be equal to or greaterthan 70% of the total flux of the light bulb.

Staying on FIG. 1, the linear array of LED devices 102 is made to beenclosed by the enclosure 108 in a variety of ways. In some embodiments,the enclosure 108 is formed directly on the linear array of LED devices102 by dispensing a binder material such as liquid polymer coatingcontaining various particles on the LED device 102. Simple as this mayseem, the coating formed this way could be unduly thick or undesirablynonuniform. In other embodiments, the enclosure 108 is fabricated andtested independently of the linear array of LED devices 102.Subsequently, the enclosure 108 is adhesively bonded to the linear arrayof LED devices 102. Bonding may be direct via a single adhesive layer orvia one or more intermediate adhesive layers to form the LED filament100 in a unitary structure comprising the linear array of LED devices102 and the enclosure 108. In an embodiment, the enclosure 108 iscombined with the LED device 102 at wafer level. Alternatively, theenclosure 108 is mounted onto an individual LED dice. The cost formaking the LED filament 100 decreases when we form the enclosure 108separately because defective enclosures 102 can be identified anddiscarded before packaging. Optionally, the enclosure 108 is sized tofit the lighting surface of the LED device 102.

FIG. 4 is a cut-open view of the LED filament in accordance of anexemplary embodiment of the present invention. In FIG. 4, a portion ofthe LED filament 100 is axially sliced and disemboweled to show theinner surface Si of the enclosure 108. In the embodiment, the enclosure108 includes an outer surface So and an inner surface Si. The outersurface So interfaces the air and the enclosure 108. When the lineararray of LED devices 102 is conformally wrapped around by the enclosure108, the inner surface Si interfaces the enclosure 108 and the lineararray of LED devices 102. When the linear array of LED devices 102 isspaced apart from the enclosure 108, the inner surface Si interfaces theenclosure 108 and the filler in the space between the linear array ofLED devices 102 and the enclosure 108 such as the air. In an embodiment,the enclosure 108 includes a texturized or patterned surface forimproving light extraction. In some embodiments, the enclosure 108includes an outer surface So texturized to interface the air and theenclosure 108. In other embodiments, the enclosure 108 includes an innersurface Si texturized to interface the enclosure 108 and the adjacentmedium such as the LED device 102 or the air.

Going back to FIG. 1, the electrical connector 506, which iselectrically connected to the linear array of LED devices 102, isconfigured to receive electrical power for energizing the linear arrayof LED devices 102. The number, shape and position of the electricalconnector 506 depends on intended purposes of an application. FIGS. 5Ato 5D show a truncated LED filament 100 to highlight the electricalconnector 106. In FIG. 5A, the electrical connector 506o includes ametallic pin electrically connected to the linear array of LED devices102. A portion of the pin is rooted in the enclosure 108 in electricalconnection with the linear array of LED devices 102. The other portionof the pin sticks out from the enclosure 108 for receiving electricalpower. Alternatively, in FIG. 5B, the electrical connector 506 aincludes a metallic hook. The shank 5062 of the hook is rooted in theenclosure 108 in electrical connection with the linear array of LEDdevices 102. The throat 5061 of the hook sticks out from the enclosure108 for receiving electrical power. Alternatively, in FIG. 5C, theelectrical connector 506 b includes a metallic fastener such as binderor clip for physically and electrically attaching to the power source.Alternatively, in FIG. 5D, the electrical connector 506 c includes ametallic receptacle. The well 5064 of the receptacle is embedded in theenclosure 108 in electrical connection with the linear array of LEDdevices 102. The opening 5066 of the receptacle is pluggable by a maleelement of the power source for receiving electrical power. In someembodiments, the electrical connector 506 includes an aperture as afemale element for receiving a male element of the power source. Relatedfeatures are described in FIGS. 5A to 5J in U.S. Ser. No. 15/499,143filed Apr. 27, 2017, which is incorporated herein by reference in itsentirety.

The number of electrical connectors and their positions on the LEDfilament depend on applications. In FIG. 1, the LED filament 100includes exactly two electrical connectors 106. A first electricalconnector 506, which is attached to a first end of the enclosure 108, ispositive. A second electrical connector 506, which is attached to asecond end of the enclosure 108, is negative. In FIG. 2, the enclosure108 includes exactly two electrical connectors 106. A first electricalconnector 506 is positive and a second electrical connector 506 isnegative. However, both electrical connectors 106 are attached to a sameend of the enclosure 108. In FIG. 3, the enclosure 108 includes exactlythree electrical connectors 506 f, 506 s. A first electrical connector506 f, which is attached to a first end of the enclosure 108, is thecommon ground. A second electrical connector 506 s, which is attached toa second end of the enclosure 108, is positive. A third electricalconnector 506 s, which is also attached to the second end of theenclosure 108, is also positive. In some embodiments, the LED filament100 is configured to maintain a desired posture in the LED light bulb byand only by physically attaching the electrical connector 506 of the LEDfilament 100 to the lead wire of the LED light bulb. The LED filament100 is like an arch bridge and the lead wire abutment. The LED filament100 maintains its posture in the LED light bulb by pressing itscompression forces against the lead wire.

FIGS. 6A to 6E are diagrams of the LED device 102 configured to glow inthe LED filament 100 in, for example, FIG. 1. The LED device 102includes an LED die 102 a that comprises a diode layer D and a substrateS. The diode layer D is configured to emit light upon energization, byapplying a voltage between an anode contact A and a cathode contact Cthrough the electrical connector 506 in FIG. 1. The diode layer Dcomprises organic or inorganic materials. In inorganic devices, thesubstrate S is made of silicon carbide, sapphire or any other singleelement or compound semiconductor material. The diode layer D comprisessilicon carbide, gallium nitride, gallium arsenide, zinc oxide or anyother single element or compound semiconductor material, which may bethe same as or different from the substrate S. The thickness of thesubstrate S is between about 100 μm and about 250 μm. Thinner andthicker substrates may be used or the substrate may not be used at all.The cathode C and anode A contacts are formed of metal or otherconductors, and may be at least partially transparent, reflective orboth. In FIG. 6A, light emission takes place directly from the diodelayer D. Alternatively, in FIG. 6B, light emission takes place fromdiode layer D through the substrate S. In FIGS. 6C and 6D, the substrateS is shaped to enhance emission from sidewalls of the substrate S toprovide other desirable effects. In FIG. 6E, the substrate itself may bethinned considerably or eliminated entirely, so that only a diode layerD is present. In FIGS. 6A to 6E, the anode A and the cathode C areprovided on opposite sides of the LED die 102 a. In FIG. 6F, however,the anode A and the cathode C are provided on the same side of the LEDdie 102 a. In each of the above embodiments, the anode A and cathode Ccontacts may be of various configurations. Multiple contacts of a giventype also may be provided. The linear array of LED devices 102 areelectrically connected by electrically connecting the anode and cathodecontacts of each of the LED devices 102 in proper sequence. In someembodiments, the anode and cathode contacts are totally absent from theLED device 102, which includes a p-junction and an n-junction. Thelinear array of LED devices 102 are electrically connected byelectrically connecting the p-junction and the n-junction of each of theLED device 102 in proper sequence. FIG. 6G is a generalization of FIGS.6A to 6F. The LED device 102 comprises an LED die 102 a that includes adiode layer D of FIGS. 6A to 6F and may also include a substrate S ofFIGS. 6A to 6D. The LED device 102 is configured to emit light uponenergization through one or more electrical contacts 1044, which mayinclude the anode A and the cathode C of FIGS. 6A to 6F. The LED device102 can emit light of different colors and can also emit radiationoutside the visible spectrum such as infrared or ultraviolet. The colorof the emitted light is determined by the material properties of thesemiconductor used in the LED die 102 a. The LED die 102 a can be madefrom many different materials, e.g. gallium nitride (GaN). Referring toFIG. 6H, in an embodiment, the LED die 102 a includes a texturizedsurface. Roughening the surface of the LED die 102 a increases lightextraction of the nitride-based LED device 102. Texturization isobtainable by using plasma etching directly on the top epilayer.However, the etching process destroys a large portion of the junction,reducing the amount of area in which the light is supposed to begenerated. To avoid damaging the thin p-GaN layer, an indiumtin-oxidelayer (ITO) can be used as the roughened layer. After completing thetraditional planar GaN LED device 102, the surface of the LED die 102 ais texturized using natural lithography, in which the randomly depositedpolystyrene spheres (PSs) were distributed as a natural mask for dryetching. After the surface-texturing process, the output power of theGaN LED device 102 is significantly increased as compared to that of theconventional LED devices.

Going back to FIG. 6G, most of the electricity in the LED device 102becomes heat rather than light (about 70% heat and 30% light). Thus, itis necessary to limit the junction temperature to a value thatguarantees a desired lifetime. In some embodiments, the LED device 102comprises a high-power LED die 102 a capable of being loaded at a highvoltage but at a lower current. Other things equal, the LED device 102maintains an acceptable luminary output without comprising thermalperformance.

Staying on FIG. 6G, in some embodiments, the linear array of LED devices102 includes a plurality of LED devices 102 in which an individual LEDdie 102 a has an elongated top view approximating a hypotheticalrectangle having a longitudinal axis substantially parallel to thelongitudinal axis of the linear array of LED devices 102. Other thingsequal, the greater the aspect ratio of the hypothetical rectangle, theless likely light gets blocked by opaque components in an LED filament100 such as the electrical contact 512 and metallic wirings forconnecting the electrical contact 512. Preferably, the aspect ratio isfrom 2:1 to 10:1. Examples are 28×14 and 20×10.

The LED filament is configured to emit white light in a variety of ways.Although illustrated as having exactly one LED die 102 a in FIGS. 6A to6H, the LED device 102 may be provided to have a plurality of LED dies102 a as well, each of which may be configured to emit the same ordifferent colors of light, mounted on a common substrate S. Themulti-die device may be grouped on the substrate S in clusters or otherarrangements such that the linear array of LED devices 102 outputs adesired pattern of light. In some embodiments, the multi-die LED devicesis configured to provide white light based on the combination of thecolors of light emitted by each of its component LED dies. For example,a multi-die LED device is configured to emit light having a spectraldistribution including at least four different color peaks (i.e., havinglocal peak wavelengths in wavelength ranges corresponding to at leastfour different colors of light) to provide the white light.Alternatively, to produce white light, a plurality of LED devicesemitting light of different colors may be used. The light emitted by theplurality of LED device is combined to produce white light of a desiredintensity, color or both. For example, when red-, green- andblue-emitting LED devices are energized simultaneously, the resultingcombined light appears white, or nearly white, depending on the relativeintensities of the component red, green and blue sources. Alternatively,the light from a single-color LED device may be converted into whitelight by surrounding the LED device with a wavelength conversionmaterial, such as phosphor particles. The term “phosphor” may be usedherein to refer to any materials that absorb light at one wavelength andre-emit light at a different wavelength, regardless of the delay betweenabsorption and re-emission and regardless of the wavelengths involved.Accordingly, the term “phosphor” is used herein to refer to materialsthat are sometimes called fluorescent or phosphorescent. In general,phosphors absorb light having shorter wavelengths and re-emit lighthaving longer wavelengths. As such, some or all of the light emitted bythe LED device at a first wavelength may be absorbed by the phosphorparticles, which may responsively emit light at a second wavelength. Forexample, a single blue emitting LED device may be surrounded with ayellow phosphor, such as cerium-doped yttrium aluminum garnet (YAG). Theresulting light, which is a combination of blue light and yellow light,may appear white to an observer. In an embodiment, the LED die emitsblue light. The white light many applications require may be achieved byconverting a portion of the blue light into yellow light. When emitted,the combination of blue and yellow light appears white.

Going back to FIG. 1, the linear array of LED devices 102 iselectrically connected to emit light upon energization by applying avoltage through the electrical connector 506. Electrical connectionbetween the LED devices 102 and the electrical connector 506 is made ina variety of ways depending on the advantages an LED filament 100 isexpected to pursue. Examples include wire bonding, conductive glue,flexible printed circuit (FPC) film and any combination of the above.FIGS. 7A to 7D are side views of the linear array of LED devices 102 inthe LED filament 100 in FIG. 1. In FIG. 7A, interconnections between theLED devices 102 are made by wire bonding. Wire bonding is a method knownin the art for making interconnections between electronic components.The bonding wire 1044 is made of copper, gold or any suitable alloy. Insome embodiments, the bonding wire 1044 includes a spring between theLED devices 102 it connects. When the linear array of LED devices 102 isstretched or compressed in the LED filament, the bonding wire 504 a,when functioning like a spring, absorbs the mechanical energy that couldotherwise open the circuit or damage the structure of the linear arrayof LED devices 102. Generally, the greater the sinuosity of the bondwire 504 a, the more mechanical energy the bond wire 504 a is capable ofstoring. The sinuosity is the ratio of the curvilinear length along thebond wire 504 a to the Euclidean distance between the end points of thebond wire 504 a. Preferably, the sinuosity is from 2 to 8. Mostpreferably, the sinuosity is from 3 to 6. In FIGS. 7B and 7C, thebonding wire 504 b, 504 c includes a bow-shaped spring between the LEDdevices 102 it connects. In FIG. 7D, the bonding wire 504 d includes ahelical spring between the LED devices 102 it connects.

Staying on FIGS. 7A to 7D, when the enclosure is formed directly on thelinear array of LED devices 102 by dispensing a liquid binder such aspolymer coating on the LED device 102, a variety of incidents maynegatively impact the quality of the LED filament produced through wirebonding. During wire bonding, the bonding wire is attached at both endsto the ohmic contacts of the LED device 102 using a combination ofdownward pressure, ultrasonic energy, and in some cases heat, to make aweld. The LED device 102 could be inadvertently shattered or burnedduring wire bonding. Moreover, ohmic contacts of the LED device 102, ifhaving a tarnished or uneven surface, will compromise bond strength andpotentially subject the LED filament to failures. Furthermore, thebonding could be dislocated when the liquid polymer is being dispensedon the bonding wire 1044 attaching, otherwise properly or improperly, tothe adjacent LED devices 102. To mitigate such problems, in someembodiments, interconnections between the LED devices 102 are made withglue wires made from electrically conductive glue continuously appliedbetween the anode and cathode contacts of adjacent LED devices 102.Electrically conductive glue is formed by doping electrically conductiveparticles in an elastic binder. The electrically conductive particle canbe gold or silver. Preferably, the electrically conductive particle ismade from optically transmissive materials such as nano-silver,nano-carbon tubes and graphene. In some embodiments, wavelengthconversion particles are blended in the electrically conductive glue forenhanced light conversion. The elastic binder can be silicone, epoxy orpolyimide. Preferably, the elastic binder for the electricallyconductive glue is made from the same material from which the enclosureis made. The glue wire is thus seamlessly integrated into the enclosureand is made capable of stretching or compressing in perfect sync withenclosure. The glue wire can be fabricated with the aid of gluedispenser capable of 3-D maneuvers.

FIGS. 8A and 8B are side views of the linear array of the LED devices102 in the LED filament in FIG. 1 where, for example, the anode A andcathode C contacts are provided on the same side of the LED die 102 a.In FIG. 8A, the glue wire 516 connecting the adjacent LED devices 102covers substantially the entire surface of the anode A and cathode Ccontacts. In FIG. 8B, the glue wire 516 connecting the adjacent LEDdevices 102 covers a portion of the surfaces of the anode A and cathodeC contacts while leaving the other portion of the surfaces uncovered.FIGS. 8C and 8D are top views of the linear array of LED devices 102 inthe LED filament in FIG. 1 where the anode A and cathode C contacts areprovided on the same side of the LED die 102 a. In FIGS. 8A and 8B, theglue wire 516 follows a substantially straight line to connect theadjacent LED devices 102. In some embodiments, the glue wire 516includes a curve of any kind for absorbing potentially destructivemechanical energy. Preferably, the sinuosity of the curve is from 3 to8. Most preferably, the sinuosity of the curve is from 2 to 6. In FIG.8C, the glue wire 516 is drawn to define an S-shaped curve between theLED devices 102 it connects in anticipation of deformation resultingfrom the LED filament being stretched or compressed. In FIG. 8D, whenthe anode A and cathode C contacts are not exactly aligned along thelongitudinal axis of the linear array of the LED devices 102, the gluewire 516 makes a turn—for example—at the corner of the LED device 102 tocomplete the electrical connection for the adjacent LED devices 102.FIGS. 8E and 8F are side views of the linear array of LED devices 102 inthe LED filament in FIG. 1 where the anode A and cathode C contacts areprovided on the same side of the LED die 102 a. In FIG. 8E, the lineararray of LED devices 102 includes a plurality of platforms 438 to fillthe gap between the adjacent LED devices 102. Preferably, the platform438 is made from the same material from which the enclosure is made. Theupper surface of the platform 438 provides a continuous path for theglue wire 516 to run from the anode A contact of the LED device 102 tothe cathode C contact of the adjacent LED devices 102. In FIG. 8F,alternatively, a mold 920 is made to follow the contour of the anode Aand cathode C contacts of the linear array of LED devices 102. The mold920, when properly deployed, defines a gap between the mold 920 and thelinear array of LED devices 102. The glue wire 516 is formed by fillingthe gap with electrically conductive glue. In some embodiments, theanode A and cathode C contacts—potentially blocking light where they aredisposed over the diode region—are eliminated from the LED die 102 a.The glue wire 516 is thus configured to connect the p-junction of an LEDdevice 102 and the n-junction of an adjacent LED devices 102.

In yet another embodiment, interconnections between the LED devices ismade with a strip of flexible printed circuit (FPC) film. FIG. 9A is atop view of the FPC film 432 prior to connecting with the linear arrayof LED devices and the electrical connector. FIG. 9B is a top view ofthe FPC film 432 after connecting with the linear array of LED devices102 and the electrical connector 506. The strip of FPC film 432 includesa plurality of conductive tracks 524 laminated onto a strip of thin andnonconductive substrate 430. The strip of FPC film 432 mechanicallysupports the linear array of LED devices 102 with the strip ofnonconductive substrate 430. The conductive track 524 electricallyconnects the linear array of LED devices 102 by connecting the anode Acontact of the LED device 102 to the cathode contact C of the adjacentLED device 102. In an embodiment, the non-conductive substrate 430 is anoptically transmissive film, preferably having optical transmittance of92% or more. For example, the nonconductive substrate 430 is a thin filmmade from Polyimide. The conductive track 524 is made from electricalconductors such as copper, copper alloy, indium tin oxide (ITO), silvernanoparticles or carbon nanotubes (CNTs). In an embodiment, theconductive track 524 is made from silver nanoparticles doped with goldfor reliable connection with the ohmic contacts of the LED device 102.The conductive track 524 comes in many patterns when observed from thetop. For example, in FIG. 9A the conductive track 524 defines a set ofslanted parallel lines. In FIG. 9B, the conductive track 524 defines aslanted grid. Preferably, the conductive track 524 has a thickness offrom 1 nm to 1 mm. Preferably, the line in the set of the parallel linesand in the grid has a width of from 1 μm to 1 mm. Some light is blockedby the conductive track 524 even when the conductive track 524 is madefrom transparent materials such as ITO. In some embodiments, theplurality of conductive tracks 524 cover less than 100% of thenonconductive substrate 430 to maximize the light traveling both waysthrough the nonconductive substrate 430. Preferably, the ratio of thetotal area covered by the plurality of conductive tracks 524 to the areaof the FPC film 432 is from 0.1% to 20%. The strip of FPC film 432 issuitable for the LED filament designed to be bendable or flexible. Whenthe conductive track 524 is properly patterned, e.g. a set of slantedparallel lines, a reliable electrical connection for the linear array ofLED devices 102 is assured because a broken line in the set of slantedparallel lines would not open the electrical connection. Relatedfeatures are described in FIGS. 33 to 43E in U.S. Ser. No. 15/499,143filed Apr. 27, 2017.

FIGS. 10A to 10C are side views of an LED filament in accordance with anexemplary embodiment of the present invention. Referring to FIGS. 10A to10C, the method of making the LED filament 100 includes the followingsteps:

S20: Arrange a linear array of LED devices 102 spaced apart from oneanother and an electrical connector 506 on a mount surface Ms;

S22: Electrically and physically connect the linear array of LED devices102 and the electrical connector 506; and

S24: Dispose the linear array of LED devices 102 in an enclosure 108.

S20 and S22 have been performed in FIG. 10A. S24 is being performed inFIG. 10B. In FIG. 10C, S20, S22 and S24 have all been performed. Themount surface Ms is any surface capable of supporting the linear arrayof LED devices 102 and the electrical connector 506 throughout the stepsof the method. Usually, the mount surface Ms is a substantially planarsurface. In some embodiments, the mount surface Ms is a threedimensional surface whose shape depends on a desired totality ofconsiderations such as: the posture the LED filament 100 is expected tomaintain in the LED light bulb; the posture each individual LED device102 is expected to maintain in relation to the rest of the linear arrayof LED devices 102; the shape of the enclosure 108; the texture of theouter surface of the enclosure 108; and the position of the linear arrayof LED devices 102 in the enclosure 108. Each one of the linear array ofLED devices 102 is properly aligned with the adjacent LED device 102 onthe mount surface Ms depending on the location of the anode and cathodecontacts on the LED device 102 and depending on the type of electricalconnection (in parallel or in series) to be made for the linear array ofLED devices 102 in S22. In S22, the electrical connection is made withbond wire, conductive glue, FPC film or a combination of the above. Thelinear array of LED devices 102 is electrically connected in parallel,in series or in a combination of both ways.

In some embodiments where a cluster of LED filaments 100 is assembled ona large mount surface Ms, the method of making an LED filament 100further includes the following step:

S26: Depanel the cluster of LED filaments 100.

In S26, an LED filament 100 depaneled from the cluster includes a lineararray of LED devices 102 or a plurality of linear arrays of LED devices102 depending on the application.

Staying on FIGS. 10A, 10B and 10C, in an embodiment, the enclosure 108is made from a cured transparent binder (i.e. adhesive) such as a curedtransparent polymer. The enclosure 108 includes a first portion 108 a,which is made first; and a second portion 108 b, which is made later.The first portion 108 a of the enclosure 108 may or may not bestructurally or otherwise distinguishable from the second portion 108 bof the enclosure 108. The mount surface Ms in S20 is provided by a panelseparable from the linear array of LED devices 102. The panel is made ofsuitable solid materials such as glass or metal. In some embodiments,the panel further includes a side wall for containing and sometimesshaping the enclosure 108 on the panel especially when, for example, apre-curing liquid polymer is dispensed on the panel duringmanufacturing. In an embodiment, S24 includes the following steps:

S240: Dispense a fist strip of transparent polymer over the linear arrayof LED devices 102;

S242: Reverse the linear array of LED devices 102 on the panel; and

S244: Dispense a second strip of transparent polymer over the lineararray of LED devices 102.

Staying on FIGS. 10A, 10B and 10C, in S240, the first strip of liquidpolymer is dispensed over the linear array of LED devices 102 to formthe first portion 108 a of the enclosure 108. Surface tension, which atthe size of an LED device 102 is large in relation to gravitationalforces, in combination with viscosity allows the strip of liquid polymerto conformally cover all corners of the linear array of LED devices 102,including the gaps between the LED devices 102. It is desirable to do afast cure, such as a UV cure, because the normal drop in viscosityduring a thermal cure would cause most liquid polymers to flow away fromthe linear array of LED devices 102. In S242, the linear array of LEDdevices 102, which is now at least partially enclosed by the firstportion 108 a of the enclosure 108, is flipped over on the panel andremains unharmed without additional care if the linear array of LEDdevices 102 was not adhesively attached to the panel in S20. In someembodiments, the linear array of LED devices 102 was adhesively attachedon the panel with adhesive materials such as photoresist forsemiconductor fabrication and die bond glue. The linear array of LEDdevices 102 can be separated from the panel after dissolving theadhesive material with proper solvents such as acetone. Residuals ofadhesive material remaining on the linear array of LED devices 102 areflushed away before moving on to S244. In S244, like in S240, the secondstrip of liquid polymer is dispensed over the linear array of LEDdevices 102, which has been enclosed, at least partially, by the firstportion 108 a of the enclosure 108. The second strip of liquid polymeris then cured and forms the second portion 108 b of the enclosure 108.We now have an LED filament 100 comprising the linear array of LEDdevices 102 disposed in the enclosure 108 operable to emit light whenenergized through the electrical connector 506.

Shifting to FIGS. 11A, 11B and 11C, in another embodiment, the enclosure108 is made from, for example, cured transparent polymer. However, themount surface Ms in S20 for the linear array of LED devices 102 and theelectrical connector 506 is provided by a strip of cured transparentpolymer that will form the first portion 108 a of the enclosure 108. S20includes the following steps:

S200: Dispense a first strip of transparent polymer on a panel 934; and

S202: Arrange a linear array of LED devices 102 spaced apart from oneanother and an electrical connector 506 on the first strip oftransparent polymer.

In the embodiment, S24 includes the following step:

S244: Dispense a second strip of transparent polymer over the lineararray of LED devices 102.

S200 has been performed in FIG. 11A. S202 has been performed in FIG.11B. S244 has been performed in FIG. 11C. In S200, the first strip ofliquid polymer is dispensed on a panel 934. The first strip of liquidpolymer is then cured on the panel 934 to form the first portion 108 aof the enclosure 108. The mount surface Ms in S20 is provided by thefirst strip of cured polymer to separable from the panel 934. The firstportion 108 a of the enclosure 108 provides a surface capable ofsupporting the linear array of LED devices 102 and the electricalconnector 506 throughout the steps of the method. The panel 934 is madeof suitable solid materials such as glass or metal. In some embodiments,the panel 934 further includes a side wall for containing and sometimesshaping the enclosure 108 on the panel 934 especially when, for example,pre-curing liquid polymer is dispensed on the panel 934 duringmanufacturing. In S202, to strengthen the combination when the lineararray of LED devices 102 and the electrical connector 506 are disposedon the first portion 108 a of the enclosure 108, optionally, an uppersurface of the first portion 108 a of the enclosure 108 is melted beforethe linear array of LED devices 102 and the electrical connector 506 aredisposed on the first portion 108 a of the enclosure 108. The lineararray of LED devices 102 and the electrical connector 506 are thus atleast partially immersed into the first portion 108 a of the enclosure108 before the upper surface of the first portion 108 a of the enclosure108 cools down and hardens. In S244, like in S200, the second strip ofliquid polymer is dispensed over the linear array of LED devices 102,which has been disposed on or at least partially enclosed by the firstportion 108 a of the enclosure 108. The second strip of liquid polymeris then cured and forms the second portion 108 b of the enclosure 108.The linear array of LED devices 102, which is now enclosed by theunitary structure of the first portion 108 a of the enclosure 108 andthe second portion 108 b of the enclosure 108, can be removed from thepanel 934 and remains unharmed without additional care if the firstportion 108 a of the enclosure 108 was not adhesively attached to thepanel 934. In some embodiments, the first portion 108 a of the enclosure108 was adhesively attached to the panel 934 with adhesive materialssuch as photoresist for semiconductor fabrication and die bond glue. Thefirst portion 108 a of the enclosure 108 can be separated from the panel934 after dissolving the adhesive material with proper solvents such asacetone. Residuals of adhesive material remaining on first portion 108 aof the enclosure 108 are then flushed away. We now have an LED filament100 comprising the linear array of LED devices 102 disposed in theenclosure 108 operable to emit light when energized through theelectrical connector 506.

Staying on FIGS. 11A, 11B and 11C, to serve as the mount surface Ms inS20 for the linear array of LED devices 102 and the electrical connector506, the first portion 108 a of the enclosure 108 in S200 is configuredto be capable of withstanding potential impact resulting frommanufacturing procedures such as wire bonding. In an embodiment, thefirst portion 108 a of the enclosure 108 comprises a hardener having apre-determined concentration of particles harder than the liquid polymerin which the particles are embedded. For example, light conversionparticles such as phosphor participles are harder than the bindermaterials such as silicone and resin. Thus, the first portion 108 a ofthe enclosure 108 can be made harder by increasing the concentration ofthe light conversion particles embedded in the transparent binder. Forexample, the first portion 108 a of the enclosure 108 is configured tohave a Shore hardness of from D20 to D70 when the ratio of the volume ofthe light conversion particles in the first portion 108 a of theenclosure 108 to the volume of the transparent binder in the firstportion 108 a of the enclosure 108 is from 20% to 80%. Alternatively,the ratio of the weight of the light conversion particles in the firstportion 108 a of the enclosure 108 to the weight of the transparentbinder in the first portion 108 a of the enclosure 108 is from 20:80 to99:1. In yet another embodiment, the first portion 108 a of theenclosure 108 is thickened such that the thickness enables the firstportion 108 a of the enclosure 108 to withstand potential impactresulting from manufacturing procedures such as wire bonding.Preferably, the thickness of the first portion 108 a of the enclosure108 is from 0.01 to 2 mm. Most preferably, the thickness of the firstportion 108 a of the enclosure 108 is from 0.1 to 0.5 mm.

Shifting to FIGS. 12A, 12B, 12C and 12D, in yet another embodiment, theenclosure 108 is made from, for example, cured transparent polymer.However, the mount surface Ms in S20 for the linear array of LED device102 and the electrical connector 506 is provided by a strip of curedtransparent polymer that will form a first portion 108 a of theenclosure 108. S20 includes the following steps:

S210: Dispense a first strip of transparent polymer on a panel 934;

S212: Dispose a strip of FPC film 432 on the first strip of transparentpolymer; and

S214: Arrange a linear array of LED devices 102 spaced apart from oneanother and an electrical connector 506 on the strip of FPC film 432.

In the embodiment, S24 includes the following step:

S244: Dispense a second strip of transparent polymer over the lineararray of LED devices 102.

S210 has been performed in FIG. 12A. S212 has been performed in FIG.12B. S214 has been performed in FIG. 12C. S244 has been performed inFIG. 12D. In S210, the first strip of liquid polymer is dispensed on apanel 934. The panel 934 is made of suitable solid materials such asglass or metal. In some embodiments, the panel 934 further includes aside wall for containing and sometimes shaping the enclosure 108 on thepanel 934 especially when, for example, pre-curing liquid polymer isdispensed on the panel 934 during manufacturing. The first strip ofliquid polymer is then cured on the panel 934 to form the first portion108 a of the enclosure 108. The mount surface Ms in S20 is provided bythe first strip of cured polymer separable from the panel 934. The firstportion 108 a of the enclosure 108 provides a surface capable ofsupporting the linear array of LED devices 102 and the electricalconnector 506 throughout the steps of the method. In 5212, to strengthenthe combination when the strip of FPC film 432 is disposed on the firstportion 108 a of the enclosure 108, optionally, an upper surface of thefirst portion 108 a of the enclosure 108 is melted. The strip of FPCfilm 432 is then at least partially immersed into the first portion 108a of the enclosure 108 before the upper surface cools down and hardens.In some embodiments, the strip of FPC film 432 includes a linear arrayof apertures 432 p punched by, for example, a stamping press.Optionally, the aperture 432 p is dimensionally smaller than the LEDdevice 102. In these embodiments, each of the linear array of LEDdevices 102 straddles exactly one of the linear array of the apertures432 p. Thus, light coming from the linear array of LED devices 102 willnot be blocked by the strip of FPC film 432. In S22, a combination ofwire bonding and FPC film 432 is employed to electrically and physicallyconnect the linear array of LED devices 102. The bonding wire 504 isattached to a conductive track 524 of the strip of FPC film 432 at itsfirst end and is attached to an ohmic contact of the LED device 102 atits second end. In 5244, like in 5210, the second strip of liquidpolymer is dispensed over the linear array of LED devices 102, which hasbeen disposed on or at least partially enclosed by the first portion 108a of the enclosure 108. The second strip of liquid polymer is then curedand forms the second portion 108 b of enclosure 108. The linear array ofLED devices 102, which is now enclosed by the unitary structure of thefirst portion 108 a of the enclosure 108 and the second portion 108 b ofthe enclosure 108, can be removed from the panel 934 and remainsunharmed without additional care if the first portion 108 a of theenclosure 108 was not adhesively attached to the panel 934. In someembodiments, the first portion 108 a of the enclosure 108 is adhesivelyattached to the panel 934 with adhesive materials such as photoresistfor semiconductor fabrication and die bond glue. The first portion 108 aof the enclosure 108 can be separated from the panel 934 afterdissolving the adhesive material with proper solvents such as acetone.Residuals of adhesive material remaining on the first portion 108 a ofthe enclosure 108 are flushed away. We now have an LED filament 100comprising the linear array of LED devices 102 disposed in the enclosure108 operable to emit light when energized through the electricalconnector 506.

FIG. 13 is a perspective view of the LED filament in accordance with anexemplary embodiment of the present invention. In FIG. 13, the line L-Lcuts the LED filament 100 radially right along a lateral surface 102 s 1of the LED device 102. Likewise, the line M-M cuts the LED filament 100radially right along the other lateral surface 102 s 2 of the LED device102. FIG. 14 is a perspective view showing the cross section of the LEDfilament 100 cut by the line L-L and the line M-M. Carved out along thecross section in FIG. 14, FIGS. 15 to 17 show a cutaway from the LEDfilament 100 defined by the line L-L and the line M-M. In someembodiments, the enclosure 108 is a tubular structure having exactly onelayer or a plurality of distinct layers. In the embodiment in FIG. 16,the enclosure 108 has exactly one layer over the LED device 102. In theembodiment in FIG. 15, the enclosure 108 is a multi-layered structureover the LED device 102. Each layer of the enclosure 108 is configuredto add a distinctive function to the LED filament 100 in FIG. 14. Forexample, the enclosure 108 in FIG. 15 includes three layers 108 c, 108 mand 108 t.

FIG. 16 shows a cutaway of the LED filament 100 in FIG. 14 in which theenclosure 108 has exactly one unitary layer over the LED device 102. Inan embodiment, the LED device 102 has a texturized light emissionsurface 102 s to increase light extraction from the diode layer of theLED device 102 by reducing total internal reflection. The light emissionsurface 102 s includes the surface of the diode layer D of the LEDdevice 102, the surface of the substrate S of the LED device 102 orboth. The light emission surface 102 s is treated with subtractiveprocesses such as etching, cutting and grinding wherein material isremoved from the light emission surface 102 s to create the desiredtexture.

Staying on FIG. 16, the enclosure 108 further includes a wavelengthconverter. The wavelength converter 420 p includes a transparent binder422 in which a plurality of light conversion particles 424, such asphosphor particles, are embedded. The phosphor particles may be formedfrom any suitable phosphor capable of converting light of one wavelengthinto another wavelength. Cerium(III)-doped YAG is often used forabsorbing the light from the blue LED device 102 and emits in a broadrange from greenish to reddish, with most of output in yellow. Thisyellow emission combined with the remaining blue emission gives thewhite light, which can be adjusted to color temperature as warm(yellowish) or cold (blueish) white. The pale yellow emission of theCe3+:YAG can be tuned by substituting the cerium with other rare earthelements such as terbium and gadolinium and can even be further adjustedby substituting some or all of the aluminium in the YAG with gallium.Alternatively, some rare-earth doped Sialons are photoluminescent andcan serve as phosphors. Europium(II)-doped β-SiAlON absorbs inultraviolet and visible light spectrum and emits intense broadbandvisible emission. Its luminance and color does not change significantlywith temperature, due to the temperature-stable crystal structure. Thus,it is suitable for using as green down-conversion phosphor forwhite-light LED filaments; a yellow variant is also available. Togenerate white light, a blue LED device is used with a yellow phosphor,or with a green and yellow SiAlON phosphor and a red CaAlSiN3-based(CASN) phosphor. In an embodiment, the wavelength conversion layer isconfigured to convert light emitting from the LED device into lighthaving a color temperature from 2400 to 2600 K by, for example,embedding in the transparent binder an appropriate combination ofyellow-and-green phosphor and red phosphor.

Staying on FIG. 16, the amount of light absorbed and re-emitted by thelight conversion particles is generally proportional to the amount oflight conversion particles 424 that the light passes through beforeegressing the LED filament. However, if the light passes through toomuch light conversion particles 424, part of the re-emitted light can beblocked from emitting from the LED filament, by the excess lightconversion particles 424. This reduces the overall light emittingefficiency of the LED filament. The amount of light conversion particles424 that the LED light passes through can be varied by varying theconcentration of light conversion particles 424, the thickness of thewavelength converter 420 p, or both. In an embodiment, light from thelinear array of LED devices 102 passes through sufficient lightconversion particles 424 so that substantially all of the light isabsorbed by the light conversion particles and re-emitted at a differentwavelength of light. At the same time, the re-emitted light does notpass through an excess light conversion material so that the re-emittedlight is not blocked from emitting from LED filament. By providingsufficient light conversion particles 424 to provide full conversionwithout blocking, the light conversion particles are in state of optimalconversion. The amount of light conversion particles 424 for optimalconversion depends on the size and luminous flux of the LED filament.The greater the size and luminous flux, the greater the amount of lightconversion particles 424 needed. Under optimal conversion, the lightemitted from the LED filament is composed primarily of photons producedby the light conversion particles 424. Preferably, the ratio of thevolume of the light conversion particles 424 in the wavelength converter420 p to the volume of the transparent binder 422 in the wavelengthconverter 420 p is from 20:80 to 99:1. Preferably, the ratio of theweight of the light conversion particles 424 in the wavelength converter420 p to the weight of the transparent binder 422 in the wavelengthconverter 420 p is from 20% to 50%. In some embodiments, however, it maybe desirable to allow a small portion of the light to be transmittedthrough the light conversion particles 424 without absorption forpurposes of modifying the chromaticity of the resulting radiation of theLED filament. For example, the LED filament emits less than 10% of theemission power of primary radiation in the absence of the lightconversion particles 424. In other words, the light conversion particles424 absorb 90% or more of the light from the linear array of LED devices102.

FIGS. 19A, 19B and 19C show a cross section of the LED filament inaccordance with an exemplary embodiment of the present invention.Referring to FIG. 19A, suitable materials for the transparent binder 422include silicone, resin and epoxy. However, these materials, having athermal conductivity from 0.01 to 2 W/(m·K), are poor thermal conductorsin relation to the light conversion particles 424 like phosphor, whichhas a thermal conductivity of from 1 to 20 W/(m·K). Excess heat trappedinside the enclosure 108 compromises the performance of theheat-sensitive LED devices 102. Moreover, the transparent binder 422,when bathed in excess heat, becomes brittle and unpleasantly yellow overtime. Thus, it is desirable to configure the wavelength converter 420 pin a way heat from the LED device 102 is efficiently transferred awayfrom the wavelength converter 420 p. In an embodiment, the wavelengthconverter 420 p further includes a plurality of heat transfer paths 444extending in a substantially radial direction for transferring heat fromthe LED device 102 away from the wavelength converter 420 p. In FIG.19A, the concentration of light conversion particles 424 in thetransparent binder 422 is so low that the heat transfer paths are mostlybroken because the majority of light conversion particles 424, sealed bythe transparent binder 422, are far apart from one another. By contrast,in FIG. 19B, the concentration of the light conversion particles 424 ishigh enough for the light conversion particles 424 to form a pluralityof heat transfer paths 444 by lining up the light conversion particles424 successively along a substantially radial direction because themajority of the light conversion particles 424, not being completelysealed by the transparent binder 422, are at least partially in directcontact with neighboring light conversion particles 424 on a same lighttransfer path 444. Preferably, the ratio of the volume of the lightconversion particles 424 in the wavelength converter 420 p to the volumeof the transparent binder 422 in the wavelength converter is from 20:80to 99:1. Preferably, the ratio of the weight of the light conversionparticles 424 in the wavelength converter 420 p to the weight of thetransparent binder 422 in the wavelength converter 420 p is from 20% to50%. As previously discussed, if the light passes through too much lightconversion particles 424, part of the re-emitted light can be blockedfrom emitting through the wavelength converter 420 p by the excess lightconversion particles 424. By providing a sufficient concentration oflight conversion particles 424 for sufficient heat transfer paths 444without blocking, the light conversion particles 424 are in state ofthermal optimum. Preferably, under the thermal optimum, the ratio of thevolume of the light conversion particles 424 in the wavelength converter420 p to the volume of the transparent binder 422 in the wavelengthconverter 420 p is from 20:80 to 99:1. Preferably, the ratio of theweight of the light conversion particles 424 in the wavelength converter420 p to the weight of the transparent binder 422 in the wavelengthconverter 420 p is from 20% to 50%. Given the same concentration, theplurality of heat transfer paths 444 that otherwise would not exist ifthe light conversion particles 424 are evenly dispersed throughout thetransparent binder 422 can be formed by maneuvering the distribution ofthe light conversion particles 424 in the transparent binder 422 wherethe plurality of heat transfer paths 444 are planned. The concentrationof the light conversion particles 424 in FIG. 19C is comparable to theconcentration of the light conversion particles 424 in FIG. 19A. Aspreviously stated, the heat transfer paths 444 in FIG. 19A are mostlybroken. By contrast, in FIG. 19C, the wavelength converter 420 pincludes the plurality of heat transfer paths 444 similar in shape to aspoke having the LED device 102 as a hub. The concentration of the lightconversion particles 424 along the planned paths is high enough for thelight conversion particles 424 to form a plurality of heat transferpaths 444, e.g. like a spoke, by lining up the light conversionparticles 424 successively along a substantially radial directionbecause most light conversion particles 424 are at least partially indirect contact with neighboring light conversion particles 424 in theque. The heat transfer path 444 passes through the wavelength converter420 p in which the concentration of the light conversion particles 424is appreciably lower than the concentration of the light conversionparticles 424 that lays out the heat transfer path 444. By elevating theconcentration of the light conversion particles 424 only where the heattransfer path 444 is planned in the transparent binder 422, the heattransfer paths 444 can be obtained while mitigating the problem of lightblocking resulting from excessive concentration of the light conversionparticles 424. In some embodiments, the heat transfer path 444 furtherincludes a gap filler for tightening up the contact between the lightconversion particles 424 on the heat transfer path 444. For example, theheat transfer path 444 further includes a plurality of nanoparticlessuch as TiO₂, Al2O₃, SiO₃, ZrO₂, CaO, SrO, BaO, silicon carbide andsilicon nanoparticles. These nanoparticles, having a thermalconductivity from 10 to 50 W/(m·K), are dimensionally much smaller thanthe light conversion particles 424 that constitute the primaryingredient of the heat transfer path 444. For example, the nanoparticleis from 10 to 300 nm. Preferably, the nanoparticle is from 20 to 100 nm.The nanoparticles help close the gaps between the light conversionparticles 424 on the heat transfer path 444. Other things equal, theheat transfer path 444, when further including nanoparticles, becomes amore efficient heat conduit because the light conversion particles 424on the heat transfer path 444 are in a tighter contact with one anotherthan in the absence of nanoparticles.

Soft materials such as silicone and resin are suitable materials for thetransparent binder. A bendable LED filament is made possible with thesehighly elasto-plastic materials. However, sometimes it is desirable touse these inherently soft materials to provide an LED filament capableof self-sustained plastic deformation such that external supportstructures can be minimized or even eliminated when the LED filament isexpected to maintain a particular posture when it is connected to alighting fixture such as LED light bulb. The posture could be a straightline extending vertically, horizontally or in any other direction. Theposture could be curves of any kind, including simple curves such as arcand polygon and complex curves such as helix, petal and gift ribbon. Inan embodiment, the enclosure includes a posture maintainer such that theLED filament is capable of self-sustained plastic deformation withminimal or even no external support such as support wires usually foundin an LED light bulb. For example, the posture maintainer includes apre-determined concentration of particles harder than the transparentbinder in which the particles are embedded. Alternatively, the posturemaintainer includes a wire system, which serve as an auxiliary pieceembedded in the transparent binder. Moreover, the posture maintainerincludes an aperture system embedded in the transparent binder. Lightconversion particles such as phosphor participles are harder than thebinder materials such as silicone and resin. Thus, the enclosure can bemade harder by increasing the concentration of the light conversionparticles in the transparent binder. In an embodiment, the hardenedenclosure includes alternate coatings of the transparent binder and thephosphor particles. The enclosure is thus configured to exhibit an evenconcentration of the phosphor particles throughout the structure. Insome embodiments, the enclosure is configured to have a Young's modulusfrom 0.1×10¹⁰ to 0.3×10¹⁰ Pa. In other embodiments to be used with LEDlight bulbs, the wavelength converter is configured to have a Young'smodulus from 0.15×10¹⁰ to 0.25×10¹⁰ Pa.

In another embodiment, the posture maintainer includes a wire systemembedded in the transparent binder to reinforce the enclosure comprisingprimarily elastic binder materials such as silicone or resin. The wireis made from resilient materials such as copper and glass fiber andpreferably light transmissive materials such as nanotubes. FIGS. 20A to20E are perspective views of a truncated LED filament 100 in accordancewith an exemplary embodiment of the present invention. The wire system170 comes in many structures of 2-D (e.g. FIGS. 20A to 20B) or 3-D (e.g.FIGS. 20C to 20E) depending on the application. In FIG. 20A, the wiresystem 170 includes a simple set of straight wires extendinglongitudinally in the enclosure 108 of the LED filament 100. In FIG.20B, the wire system 170 includes a set of sinuous springs extendinglongitudinally in the enclosure 108. In FIG. 20C, the wire system 170includes a helical spring extending longitudinally in the enclosure 108of the LED filament 100. In FIGS. 20D and 20E, the wire system 170includes a grid structure extending in the enclosure 108 along thelongitudinally axis of the LED filament 100. In FIG. 20D, the wiresystem 170 includes a rectilinear grid extending in the enclosure 108along the longitudinally axis of the LED filament 100. In FIG. 20E, thewire system 170 includes a curvilinear grid extending in the enclosure108 along the longitudinally axis of the LED filament 100. Relatedfeatures may be referred to FIG. 55 to FIG. 55F in application of U.S.Ser. No. 15/499,143 filed Apr. 27, 2017.

In yet another embodiment, the posture maintainer includes an aperturesystem beneath the surface of the enclosure where tight turns areplanned for the posture the LED filament is expected to maintain in anapplication. FIGS. 20G and 20F show a truncated LED filament, when it isleft straight and when it is bent to maintain a posture in the LED lightbulb, in accordance with an exemplary embodiment of the presentinvention. In FIG. 20F, for example, the LED filament 100 is expected tomaintain an S-shaped posture. A set of apertures 468 p is deployed atthe inner part of the enclosure 108 where the tight turn is planned. Theset of apertures 468 p makes it easier for the LED filament 100 tomaintain the S-shaped posture by accommodating compression at the innerpart of the tight turn. In some embodiments, the posture maintainerincludes a combination of the structures illustrated above. In FIG. 20G,the posture maintainer includes a combination of wire system 170 andaperture 468 p. The wire system includes a straight wire and a helicalspring. The helical spring is deployed in the wire system 170 only wheretight turns are planned for the posture the LED filament 100 is expectedto maintain in an application. Otherwise, only the straight wire isdeployed. A set of apertures 468 p is deployed at the inner part of theenclosure 108 where a tight turn is planned. Related features may bereferred to FIG. 57A, 57B in application of U.S. Ser. No. 15/499,143filed Apr. 27, 2017.

In an embodiment, the outer surface of the enclosure is provided by apolished layer. An LED filament having a glossy finish may beaesthetically appealing to some people. However, the LED filament maysuffer from total internal reflection or poor heat dissipation. Inanother embodiment, the outer surface of the enclosure is provided by atexturized layer. The texturized layer improves light extraction byreducing total internal reflection. The texturized layer enhances heatdissipation by providing the enclosure with a greater surface area thana polished layer does. FIGS. 21A, 21B and 21C show a cross section ofthe LED filament in accordance with an exemplary embodiment of thepresent invention. In FIG. 21A, for example, the textured layer St isformed by a sufficient concentration of the light conversion particles424 found close to but bulging from the outer surface of the enclosure108. By contrast, in FIGS. 21B and 21C, the enclosure 108 includes adedicated texturized layer St having different patterns such as wedge(FIG. 21B) and cube (FIG. 21C).

Yttrium aluminum garnet (YAG), typically having a refractive index (RI)of about 1.8, is an example of a common phosphor that may be used. TheRI of the phosphor particles and the RI of the binder material can bethe same or different. In an embodiment, the binder material includes atransparent material having an RI that is substantially matched to thatof the wavelength conversion particles embedded therein. For example,the binder material includes a high-index silicone having an RI of about1.6 or greater. By providing the wavelength conversion particles in asubstantially index-matched binder material, light scattering losses dueto differences in the RI of the binder material and the wavelengthconversion particles can be reduced or eliminated. FIG. 17 shows acutaway from the LED filament in FIG. 13. In some embodiments, aplurality of nanoparticles 426 is embedded in the transparent binder 422that formed the wavelength converter 420 p. The nanoparticles 426 aredispersed throughout the transparent binder 422 of the wavelengthconverter 420 p. By including nanoparticles 426 with a RI higher thanthat of the host medium—the transparent binder 422—the effective RI ofthe host medium is increased. The presence of nanoparticles 426 in thetransparent binder 422 brings the RI of the transparent binder 422(e.g., regular silicone with an RI of about 1.5) closer to the RI of thephosphor particles 424 (with an RI of about 1.8). When these twoelements are not closely index-matched, the difference in RI results inlight scattering because typical phosphor particles 424 aresubstantially larger (about 5.5 μm) than the wavelength of light emittedfrom the LED device 102 (450 nm for a blue LED). Light extractionefficiency increases when the difference in RI between the phosphorparticle 424 and the transparent binder 422 is reduced. However, theefficiency only increases up to a point. If the effective RI of thetransparent binder 422 gets too high, the light extraction efficiencywill decrease due to total internal reflection at the flat interface ofthe wavelength converter 420 p and any surrounding medium having a lowerRI (e.g., silicone or air). An acceptable effective RI for thewavelength converter 420 p is approximately 1.7, providing optimalindex-matching with manageable levels of total internal reflection. Thenanoparticles 426 may comprise several different materials such as TiO₂,Al₂O₃, SiO₃, ZrO₂, CaO, SrO, BaO, diamond, silicon carbide and siliconnanoparticles. The RI of both TiO₂ and diamond is approximately 2.5. Thevolume of nanoparticles 426 that is needed to adjust the effective RI ofthe wavelength converter 420 p by a certain amount can be easilycalculated using Vegard's Law which states that the relationship betweenvolume and RI is linear. For example, if the wavelength converter 1604material has a RI of 1.5 and the target effective RI is 1.7, then thewavelength converter 420 p should comprise approximately 20% TiO₂nanoparticles by volume. Other material combinations and compositionsmay also be used. For example, some embodiments may have greater than 5%nanoparticles 426 by volume. Other embodiments may have greater than 10%nanoparticles 426 by volume. Still other embodiments may include 20-40%by volume. The concentration of the nanoparticles 426 depends on suchfactors as the material being used and the desired RI adjustment.

Staying on FIG. 17, sometimes it is desirable to load the wavelengthconverter 420 p with a high volume of light conversion particles 424.There would be less space in the wavelength converter 420 p fornanoparticles 426. As discussed above, the nanoparticles 426 are used toadjust the effective RI of the wavelength converter 420 p. When thenanoparticles 426 do not produce a large enough RI shift in thewavelength converter 420 p, the spacer 4202 s can compensate for thosecases. In addition to shifting RI, the spacer 4202 s, when interposedbetween the LED device 102 and the wavelength converter 420 p, enables auniform thickness of the wavelength converter 420 p to produce uniformwhite light, which entails a proper combination of blue light and thephosphor light. However, a variety of factors cause the thickness of thewavelength converter 420 p to be uneven when the wavelength converter420 p is disposed directly over the LED device 102. The surface of theLED device might be, intentionally or unintentionally, uneven. Forexample, in FIG. 17, the wavelength converter 420 p, if disposeddirectly over the LED device 102, would be thinner at the point p1 thanat the point p2 when the surface of the LED device 102 is texturized.Moreover, the array of LED devices 102 does not define a perfectly eveninterface for the wavelength converter 420 p to sit on. Related featuresmay be referred to FIG. 59A to FIG. 59C in application of U.S. Ser. No.15/499,143 filed Apr. 27, 2017.

FIG. 18 is a cross section of a truncated LED filament 100 cut along itslongitudinal axis. In FIG. 18, for example, the wavelength converter 420p, if directly disposed over the linear array of LED devices 102, wouldbe thinner at the point p3 than at the point p4. Where the wavelengthconverter 420 p is relatively thin, blue light would dominate becausethere would be insufficient contribution of light from the phosphors.The spacer 4202 s in FIGS. 17 and 18 eliminates the problem by forming alevel interface for the wavelength converter 420 p to sit on. The spacer4202 s can be made of many different materials such as silicone, epoxy,oil, dielectrics, and other materials. The material should be chosensuch that the RI of the spacer 4202 s is smaller than the RI of the LEDdevice 102 and the RI of the wave length converter 1604. A portion ofthe light that enters the spacer 4202 s is then incident on theinterface between the spacer 4202 s and the wavelength converter 420 p.At the interface the light sees a step-up in RI and passes intowavelength converter 420 p with minimal reflection. If the light isreflected or backscattered in the wavelength converter 420 p, it willsee the RI step-down at the spacer 4202 s interface and has a finitechance of being reflected back into the wavelength converter 420 pbecause of the TIR phenomenon.

Referring to FIGS. 16 and 17, index-matching the transparent binder 422with the phosphor particles 424 reduces scattering within the wavelengthconverter 420 p. However, such reduction in scattering adversely affectsthe uniformity of the color temperature distribution in the LEDfilament. To mitigate the negative effect, a light scatterer 4202 t,e.g. light scattering particles (LSPs) 416, is disposed proximate to theLED device 102. The LSPs 416 are distributed around the LED device 102so that the individual photons are redirected before they are emitted torandomize the point where they exit the enclosure 108. This has theeffect of evening out the color temperature distribution such that anoutside observer sees roughly the same color over a broad range ofviewing angles. The LSPs 416 should have a high RI relative to thesurrounding medium, creating a large RI differential between thematerials. Because the RI differential causes refraction, it would alsobe possible to use an LSP material that has a low RI relative to thesurrounding medium. The LSPs 416 create localized non-uniformities inthe medium that force the light to deviate from a straight path. Whenthe light strikes one or more of the light scattering particles 416 theRI differential between the medium and the particles causes the light torefract and travel in a different direction. A large RI differentialyields a more drastic direction change for an incident photon. For thisreason, materials with a high RI work well in mediums such as siliconeor epoxy. Another consideration when choosing a light scatteringmaterial is the optical absorbance of the material. Large particlesbackscatter more of the light inside the package before it can escapethe device, decreasing the total luminous output of the device. Thus,preferred scattering particle 416 materials have a high RI relative tothe medium and a particle size comparable to the wavelength of the lightpropagating through the host medium. Ideally, LSPs 416 ensure maximumforward or sideways scattering effect for a given spectrum whileminimizing light loss due to backscattering and absorption. The LSPs 416can comprise many different materials, e.g., silica gel, siliconnanoparticles and zinc oxide (ZnO). Various combinations of materials orcombinations of different forms of the same material may be used toachieve a desired scattering effect. Various percentages of compositionof the LSPs 416 can be used as dictated by the application. Depending onthe materials used, the LSPs 416 will typically be found inconcentrations ranging from 0.01% to 5% by volume. Other concentrationscan be used; however, the loss due to absorption increases with theconcentration of the scattering particles. Thus, the concentrations ofthe LSPs 416 should be chosen to maintain an acceptable loss figure. Insome embodiments, the light scattering particles 416 have diameters thatrange from 0.1 μm to 2 μm. In some cases, it may be desirable to useLSPs 416 of different sizes. For example, in one embodiment a firstplurality of LSPs 416 may comprise titania, silica and diamond, and asecond plurality of LSPs 416 may comprise fused silica, titania anddiamond. Many other combinations are possible to achieve a desired colortemperature distribution.

The light scatterer, i.e. the LSPs, can be disposed anywhere in the LEDfilament so long as they are proximate to the LED device such thatsubstantially all of the emitted light has a good probability ofinteracting with the LSPs. In FIGS. 16 and 17, the light scatterer 4202t and the wavelength converter 420 p merge into one layer in theenclosure 108. The LSPs 416 are dispersed throughout the binder material1600 along with the nanoparticles 426 and the phosphor particles 424.Because the light scatterer 4202 t is disposed over the LED device 102,substantially all of the light travels through the wavelength lightscatterer 4202 t where the LSPs 416 are dispersed before egressing theenclosure 108. In other embodiments, the LSPs are dispersed throughout abinder material in a dedicated light scatterer disposed over the LEDdevice. In FIG. 22, the wavelength converter 420 p is sandwiched by thelight scatterer 4202 t and LED device 102. The LSPs 416 are dispersed inthe light scatterer 4202 t throughout the binder material (i.e.transparent binder) 422. Because the light scatterer 4202 t is disposedall over the LED device 102, all of the light, converted by wavelengthconverter 420 p, must subsequently travel through the light scatterer4202 t before egressing the enclosure 108.

In accordance with an exemplary embodiment of the claimed invention, theentire enclosure is a monolithic structure made from a single piece oflight transmissive material. Other things equal, the enclosure is thusconfigured to have a greater structural integrity under stress than anenclosure assembled from parts. In some embodiments, the entiremonolithic structure shares a uniform set of chemical and physicalproperties throughout the structure. In other embodiments, themonolithic structure exhibits diverse chemical or physical properties inan otherwise indivisible structure. For example, the monolithicstructure includes a first region and a second region having a differentset of properties (e.g. hardness, plasticity, thermal conductivity,thermal radiation power, wavelength conversion or other opticalcapability) from that of the first region. In accordance with analternative embodiment of the claimed invention, the enclosure includesa set of otherwise divisible modules interconnected to form a unitarystructure of the enclosure. Unlike a monolithic structure, the modulesin the set are made separately and then the enclosure is assembled fromthe set of modules. Each module is tested separately before beingbrought together with other modules. Thus, a defective module isdiscarded and replaced with a good one without having to abandon theentire enclosure when made of a monolithic structure but unfortunatelyhaving a defect even though of a localized nature. A module usuallyexhibits a uniform set of properties throughout the module.Alternatively, a module possesses diverse sets of properties wheredesired. For example, the module includes a first region and a secondregion having a different set of properties (e.g. hardness, plasticity,thermal conductivity, thermal radiation power, wavelength conversion orother optical capability) from that of the first region.

In the embodiments where the enclosure is a monolithic structureexhibiting diverse chemical or physical properties in an otherwiseindivisible structure, the enclosure includes a plurality of regionshaving distinctive properties to enable a desired totality of functionsfor the LED filament. The plurality of regions in the enclosure isdefined in a variety of ways depending on applications. In FIG. 23, thetruncated LED filament 100 is further sliced vertically—i.e. along thelight illuminating direction of the linear array of LED devices 102—intoequal halves along the longitudinal axis of the LED filament 100 to showits internal structure. The regions of the enclosure are defined by ahypothetical plane perpendicular to the light illuminating direction ofthe linear array of LED devices 102. For example, the enclosure 108includes three regions, 420 w, 420 m, 420 u defined by a hypotheticalpair of planes compartmentalizing the enclosure 108 into an upper region420 u, a lower region 420 w and a middle region 420 m sandwiched by theupper region 420 u and the lower region 420 w. The linear array of LEDdevices 102 is disposed exclusively in one of the regions of theenclosure 108. Alternatively, the linear array of LED devices 102 isabsent from at least one of the regions of the enclosure 108.Alternatively, the linear array of LED devices 102 is disposed in allregions of the enclosure 108. In FIG. 23, the linear array of LEDdevices 102 is disposed exclusively in the middle region 420 m of theenclosure 108 and is spaced apart by the middle region 420 m from thetop region 420 u and the lower region 420 w. In an embodiment, themiddle region 420 m includes a wavelength converter for converting bluelight emitting from the LED device 102 into white light. The upperregion 420 u includes a cylindrical lens for aligning the light beamingupwards. The lower region 420 w includes a cylindrical lens for aligningthe light beaming downwards. In another embodiment, the middle region420 m is made harder than the upper region 420 u, the lower region 420 wor both by, for example, embedding a greater concentration of phosphorparticles in the middle region 420 m than in the upper region 420 u, thelower region 420 w or both. The middle region 420 m, because it isharder, is thus configured to better protect the linear array of LEDdevices 102 from malfunctioning when the LED filament 100 is bent tomaintain a desired posture in a light bulb. The upper region 420 u (orthe lower region 420 w) is made softer for keeping the entire LEDfilament 100 as bendable in the light bulb as it requires for generatingomnidirectional light with preferably exactly one LED filament 100. Inyet another embodiment, the middle region 420 m has greater thermalconductivity than the upper region 420 u, the lower region 420 w or bothby, for example, doping a greater concentration of nanoparticles in themiddle region 420 m than in the upper region 420 u, the lower region 420w or both. The middle region 420 m, having greater thermal conductivity,is thus configured to better protect the linear array of LED devices 102from degrading or burning by removing excess heat from the LED device102. The upper region 420 u (or the lower region 420 w), because it isspaced apart from the linear array of LED devices 102, plays a lesserrole than the middle region 420 m in cooling the LED device 102. Thecost for making the LED filament 100 is thus economized when the upperregion 420 u (or the lower region 420 w) is not as heavily doped withnanoparticles as the middle region 420 m. The dimension of the middleregion 420 m, in which the linear array of LED devices 102 isexclusively disposed, in relation to the entire enclosure 108 isdetermined by a desired totality of considerations such as lightconversion capability, bendability and thermal conductivity. Otherthings equal, the bigger the middle region 420 m in relation to theentire enclosure 108, the LED filament 100 has greater light conversioncapability and thermal conductivity but will be less bendable. A crosssection perpendicular to the longitudinal axis of the LED filament 100reveals the middle region 420 m and other regions of the enclosure. R1is a ratio of the area of the middle region 420 m to the overall area ofthe cross section. Preferably, R1 is from 0.2 to 0.8. Most preferably,R1 is from 0.4 to 0.6.

In FIG. 24, the truncated LED filament 100 is further slicedhorizontally—i.e. perpendicular to the light illuminating direction ofthe linear array of LED devices 102—into equal halves along thelongitudinal axis of the LED filament 100 to show its internalstructure. The regions of the enclosure 108 are defined by ahypothetical plane parallel to the light illuminating direction of thelinear array of LED devices 102. For example, the enclosure 108 includesthree regions 420 l, 420 m, 420 r defined by a hypothetical pair ofplanes compartmentalizing the enclosure 108 into a right region 420 r, aleft region 420 l and a middle region 420 m sandwiched by the rightregion 420 r and the left region 420 l. The linear array of LED devices102 is disposed exclusively in one of the regions of the enclosure 108.Alternatively, the linear array of LED devices 102 is absent from atleast one of the regions of the enclosure 108. Alternatively, the lineararray of LED devices 102 is disposed in all regions of the enclosure108. In FIG. 24, the linear array of LED devices 102 is disposedexclusively in the middle region 420 m of the enclosure 108 and isspaced apart by the middle region 420 m from the right region 420 r andthe left region 420 l. In an embodiment, the middle region 420 mincludes a wavelength converter for converting blue light emitting fromthe LED device 102 into white light. The right region 420 r includes acylindrical lens for aligning the light beaming rightwards. The leftregion 420 l includes a cylindrical lens for aligning the light beamingleftwards. In another embodiment, the middle region 420 m is made harderthan the right region 420 r, the left region 420 l or both by, forexample, embedding a greater concentration of phosphor particles in themiddle region 420 m than in the right region 420 r, the left region 420l or both. The middle region 420 m, because it is harder, is thusconfigured to better protect the linear array of LED devices 102 frommalfunctioning when the LED filament 100 is bent to maintain a desiredposture in a light bulb. The right region 420 r (or the left region 420l) is made softer for keeping the entire LED filament 100 as bendable inthe light bulb as it requires for generating omnidirectional light with,preferably, exactly one LED filament 100. In yet another embodiment, themiddle region 420 m has greater thermal conductivity than the rightregion 420 r, the left region 420 l or both by, for example, doping agreater concentration of nanoparticles in the middle region 420 m thanin the right region 420 r, the left region 420 l or both. The middleregion 420 m, having greater thermal conductivity, is thus configured tobetter protect the linear array of LED devices 102 from degrading orburning by removing excess heat from the LED device 102. The rightregion 420 r (or the left region 420 l), because it is spaced apart fromthe linear array of LED devices 102, plays a lesser role than the middleregion 420 m in cooling the LED device 102. The cost for making the LEDfilament 100 is thus economized when the right region 420 r (or the leftregion 420 l) is not as heavily doped with nanoparticles as the middleregion 420 m. The dimension of the middle region 420 m, in which thelinear array of LED devices 102 is exclusively disposed, in relation tothe entire enclosure 108 is determined by a desired totality ofconsiderations such as light conversion capability, bendability andthermal conductivity. Other things equal, the bigger the middle region420 m in relation to the entire enclosure 108, the LED filament 100 hasgreater light conversion capability and thermal conductivity but will beless bendable. A cross section perpendicular to the longitudinal axis ofthe LED filament 100 reveals the middle region 420 m and other regionsof the enclosure 108. R2 is a ratio of the area of the middle region 420m to the overall area of the cross section. Preferably, R2 is from 0.2to 0.8. Most preferably, R2 is from 0.4 to 0.6.

In FIG. 25, the truncated LED filament 100 is further carved into asmall portion and a big portion to show its internal structure. Thesmall portion is defined by revolving the rectangle ABCD around the lineCD (i.e. the central axis of the LED filament 100) for a fraction of 360degrees. Likewise, the big portion is defined by revolving the rectangleABCD around the line CD but for the entirety of 360 degrees except forthe space taken by the small portion. The regions of the enclosure 108are defined by a hypothetical cylindrical surface having the centralaxis of the LED filament 100 as its central axis. For example, theenclosure 108 includes three regions 420 e, 420 m, 420 o defined by ahypothetical pair of coaxial cylindrical surfaces compartmentalizing theenclosure 108 into a core region 420 e, an outer region 420 o and amiddle region 420 m sandwiched by the core region 420 e and the outerregion 420 o. The linear array of LED devices 102 is disposedexclusively in one of the regions of the enclosure 108. Alternatively,the linear array of LED devices 102 is absent from at least one of theregions of the enclosure 108. Alternatively, the linear array of LEDdevices 102 is disposed in all regions of the enclosure 108. In FIG. 25,the linear array of LED devices 102 is disposed exclusively in the coreregion 420 e of the enclosure 108 and is spaced apart by the core region420 e from the middle region 420 m and the outer region 420 o. In anembodiment, the outer region 420 o includes a light scatterer forincreasing light extraction from the LED device 102 by reducing totalinternal reflection. The middle region 420 m includes a wavelengthconverter for converting blue light emitting from the LED device 102into white light. The core region 420 e includes a spacer. The spacerprevents heat coming from the LED device 102 from quickly degrading thephosphor particle in the wavelength converter by keeping the phosphorparticle apart from the LED device 102. Moreover, the spacer enables auniform thickness of the middle region 420 m, which includes thewavelength converter, to produce uniform white light, which entails aproper combination of blue light and the phosphor light. In anotherembodiment, the middle region 420 m is made harder than the core region420 e, the outer region 420 o or both by, for example, embedding agreater concentration of phosphor particles in the middle region 420 mthan in the core region 420 e, the outer region 420 o or both. Themiddle region 420 m, because it is harder, is thus configured to betterprotect the linear array of LED devices 102 from malfunctioning when theLED filament 100 is bent to maintain a desired posture in a light bulb.The core region 420 e (or the outer region 420 o) is made softer forkeeping the entire LED filament 100 as bendable in the light bulb as itrequires for generating omnidirectional light with, preferably, exactlyone LED filament 100. In yet another embodiment, the core region 420 ehas greater thermal conductivity than the middle region 420 m, the outerregion 420 o or both by, for example, doping a greater concentration ofsuch particles as nanoparticles, aluminium oxide, aluminium nitride andboron nitride in the core region 420 e than in the middle region 420 m,the outer region 420 o or both. These particles are electricalinsulators while having greater heat conductivity than phosphorparticles. The core region 420 e, having greater thermal conductivity,is thus configured to better protect the linear array of LED devices 102from degrading or burning by removing excess heat from the LED device102. The middle region 420 m (or the outer region 420 o), because it isspaced apart from the linear array of LED devices 102, plays a lesserrole than the core region 420 e in cooling the LED device 102 throughheat conduction. The cost for making the LED filament 100 is thuseconomized when the outer region 420 o (or the middle region 420 m) isnot as heavily doped with nanoparticles as the core region 420 e. Instill another embodiment, the outer region 420 o has greater thermalradiation power than the middle region 420 m, the core region 420 e orboth by, for example, doping a greater concentration of such particlesas nanoparticles, graphene, nano-silver, carbon nanotube and aluminiumnitride in the outer region 420 o than in the middle region 420 m, thecore region 420 e or both. These particles have greater thermalradiation power than the optically transmissive binder and greaterthermal conductivity than phosphor particles. The outer region 420 o,having greater thermal conductivity, is thus configured to betterprotect the linear array of LED devices 102 from degrading or burning byremoving excess heat from the LED device 102. The core region 420 e (orthe outer region 420 o), because of their weaker thermal radiationpower, plays a lesser role than the outer region 420 o in cooling theLED device 102 through thermal radiation. The cost for making the LEDfilament 100 is thus economized when the core region 420 m (or themiddle region 420 m) is not as heavily doped with nanoparticles as theouter region 420 o. These particles are electrical insulators whilehaving greater heat conductivity than phosphor particles. The coreregion 420 e, having greater thermal conductivity, is thus configured tobetter protect the linear array of LED devices 102 from degrading orburning by removing excess heat from the LED device 102. The middleregion 420 m (or the outer region 420 o), because it is spaced apartfrom the linear array of LED devices 102, plays a lesser role than thecore region 420 e in cooling the LED device 102 through heat conduction.The cost for making the LED filament 100 is thus economized when theouter region 420 o (or the middle region 420 m) is not as heavily dopedwith nanoparticles as the core region 420 e. To enhance the ability ofthe LED filament 100 to reveal colors of objects faithfully incomparison with an ideal or natural light source, in still anotherembodiment, the core region 420 e has an excitation spectrum (and/oremission spectrum) induced at shorter wavelengths than the middle region420 m, the outer region 420 o or both by, for example, doping a greaterconcentration of such particles as phosphors in the core region 420 ethan in the middle region 420 m, the outer region 420 o or both. Thecore region 420 e is responsible for converting light coming from theLED device 102 at the ultraviolet range into the visible spectrum. Otherregions 420 m, 420 o of the LED filament 100 are responsible for, bycontrast, further converting light coming from the core region 420 einto light having even longer wavelengths. In an embodiment, the coreregion 420 e is doped with a greater concentration of phosphor particlesthan the middle region 420 m, the outer region 420 o or both. The middleregion 420 m, which is optional in some embodiments, includes aluminescent dye for converting light coming from the core region 420 einto light having longer wavelengths and a lesser concentration ofphosphor particles than the core region 420 e. The outer region 420 oincludes a luminescent dye for converting light coming from the coreregion 420 e into light having longer wavelengths but includes nophosphor particles for keeping high flexibility of the LED filament 100.The dimension of the core region 420 e, in which the linear array of LEDdevices 102 is exclusively disposed, in relation to the entire enclosure108 is determined by a desired totality of considerations such as lightconversion capability, bendability and thermal conductivity. Otherthings equal, the bigger the core region 420 e in relation to the entireenclosure 108, the LED filament 100 has less light conversion capabilityand thermal conductivity but will be more bendable. A cross sectionperpendicular to the longitudinal axis of the LED filament 100 revealsthe core region 420 e and other regions of the enclosure 108. R3 is aratio of the area of the core region 420 e to the overall area of thecross section. Preferably, R3 is from 0.1 to 0.8. Most preferably, R3 isfrom 0.2 to 0.5. The dimension of the middle region 420 m, whichincludes the wavelength converter, in relation to the entire enclosure108 is determined by a desired totality of considerations such as lightconversion capability, bendability and thermal conductivity. Otherthings equal, the bigger the middle region 420 m in relation to theentire enclosure 108, the LED filament 100 has greater light conversioncapability and thermal conductivity but will be less bendable. A crosssection perpendicular to the longitudinal axis of the LED filament 100reveals the middle region 420 m and other regions of the enclosure 108.R4 is a ratio of the area of the middle region 420 m to the overall areaof the cross section. Preferably, R4 is from 0.1 to 0.8. Mostpreferably, R4 is from 0.2 to 0.5.

In FIG. 26, the truncated LED filament 100 is further carved into asmall portion and a big portion to show its internal structure. LikeFIG. 25, the small portion is defined by revolving the rectangle ABCDaround the line CD (i.e. the central axis of the LED filament 100) for afraction of 360 degrees. Likewise, the big portion is defined byrevolving the rectangle ABCD around the line CD for the entirety of 360degrees except for the space taken by the small portion. The regions ofthe enclosure 108 are defined by a hypothetical set of parallel planesintersecting the enclosure 108 perpendicularly to the longitudinal axisof the enclosure 108. For example, the enclosure 108 includes twoalternating regions 420 f, 420 s, i.e. a first region 420 f and a secondregion 420 s, defined by the hypothetical set of parallel planes. In anembodiment, the hypothetical set of parallel planes intersect theenclosure 108 right at the edges of an LED device 102. The LED device102 is disposed exclusively in the first region 420 f. The means forelectrically connecting the LED devices 102, e.g. the bond wire, isdisposed exclusively in the second region 420 s. In another embodiment,the hypothetical set of parallel planes intersect the enclosure 108between the edges of an LED device 102. A portion of the LED device 102,excluding the edges, is disposed in the first region 420 f; the otherportion of the LED device 102, including the edges, is disposed in thesecond region 420 s. A portion of the means for electrically connectingthe LED devices 102, excluding the ends of the wiring, is disposed inthe second region 420 s; the other portion of the means for electricallyconnecting the LED devices 102, including the ends of the wiring, isdisposed in the second region 420 s. In yet another embodiment, thehypothetical set of parallel planes intersect the enclosure 108 at thespace between adjacent LED devices 102. The LED device 102 is disposedexclusively in the first region 420 f. A portion of the means forelectrically connecting the LED devices 102, excluding the ends of thewiring, is disposed in the first region 420 f; the other portion of themeans for electrically connecting the LED devices 102, including theends of the wiring, is disposed in the second region 420 s. Depending onapplications, the first region 420 f is configured to have a differentset of properties from that of the second region 420 s. In anembodiment, the first region 420 f is made harder than the second region420 s by, for example, embedding a greater concentration of phosphorparticles in the first region 420 f than in the second region 420 s. Thefirst region 420 f, because it is harder, is thus configured to betterprotect the linear array of LED devices 102 from malfunctioning when theLED filament 100 is bent to maintain a desired posture in a light bulb.The second region 420 s is made softer for keeping the entire LEDfilament 100 as bendable in the light bulb as it requires for generatingomnidirectional light with, preferably, exactly one LED filament 100. Inanother embodiment, the first region 420 f has greater thermalconductivity than the second region 420 s by, for example, doping agreater concentration of nanoparticles in the first region 420 f than inthe second region 420 s. The first region 420 f, having greater thermalconductivity, is thus configured to better protect the linear array ofLED devices 102 from degrading or burning by removing excess heat fromthe LED device 102. The second region 420 s, because it is spaced apartfrom the linear array of LED devices 102, plays a lesser role than thefirst region 420 f in cooling the LED device 102. The cost for makingthe LED filament 100 is thus economized when the second region 420 s isnot as heavily doped with nanoparticles as the first region 420 f. Thedimension of the first region 420 f, in which the LED device 102 isdisposed, in relation to the entire enclosure 108 is determined by adesired totality of considerations such as light conversion capability,bendability and thermal conductivity. Other things equal, the bigger thefirst region 420 f in relation to the entire enclosure 108, the LEDfilament 100 has greater light conversion capability and thermalconductivity but will be less bendable. An outer surface of theenclosure 108 shows a combination of the first region 420 f and otherregions. R5 is a ratio of the total area of the first region 420 f foundon the outer surface of the enclosure 108 to the overall area of theouter surface of the enclosure 108. Preferably, R5 is from 0.2 to 0.8.Most preferably, R5 is from 0.4 to 0.6.

The ways illustrated above in which an enclosure is divided into regionshaving distinctive properties can be employed in combination with oneanother, in FIGS. 27 and 29 as examples, to functionalize an LEDfilament 100 as desired. In FIG. 27, the truncated LED filament 100 isfurther carved into a small portion and a big portion to show itsinternal structure. The small portion is defined by revolving therectangle ABCD around the line CD (i.e. the central axis of the LEDfilament 100) for 90 degrees. Likewise, the big portion is defined byrevolving the rectangle ABCD around the line CD for the entirety of 360degrees except for the space taken by the small portion. The enclosure108 is regionalized with, for example, three sets of hypotheticalplanes. The first set of hypothetical planes intersects the enclosure108 perpendicularly to the light illuminating direction of the lineararray of LED devices 102. For example, the enclosure 108 includes threeregions defined by a hypothetical pair of planes compartmentalizing theenclosure 108 into an upper region 420 u, a lower region 420 w and ahorizontal middle region 420 hm sandwiched by the upper region 420 u andthe lower region 420 w. The linear array of LED devices 102 is disposedexclusively in one of the regions of the enclosure 108. Alternatively,the linear array of LED devices 102 is absent from at least one of theregions of the enclosure 108. Alternatively, the linear array of LEDdevices 102 is disposed in all regions of the enclosure 108. In FIG. 27,the linear array of LED devices 102 is disposed exclusively in thehorizontal middle region 420 hm of the enclosure 108 and is spaced apartby the horizontal middle region 420 hm from the top region 420 u and thelower region 420 w. In an embodiment, the horizontal middle region 420hm includes a wavelength converter for converting blue light emittingfrom the LED device 102 into white light. The upper region 420 uincludes a cylindrical lens for aligning the light beaming upwards. Thelower region 420 w includes a cylindrical lens for aligning the lightbeaming downwards. In another embodiment, the horizontal middle region420 hm is made harder than the upper region 420 u, the lower region 420w or both by, for example, embedding a greater concentration of phosphorparticles in the horizontal middle region 420 hm than in the upperregion 420 u, the lower region 420 w or both. The horizontal middleregion 420 hm, because it is harder, is thus configured to betterprotect the linear array of LED devices 102 from malfunctioning when theLED filament 100 is bent to maintain a desired posture in a light bulb.The upper region 420 u (or the lower region 420 w) is made softer forkeeping the entire LED filament 100 as bendable in the light bulb as itrequires for generating omnidirectional light with preferably exactlyone LED filament 100. In yet another embodiment, the horizontal middleregion 420 hm has greater thermal conductivity than the upper region 420u, the lower region 420 w or both by, for example, doping a greaterconcentration of nanoparticles in the horizontal middle region 420 hmthan in the upper region 420 u, the lower region 420 w or both. Thehorizontal middle region 420 hm, having greater thermal conductivity, isthus configured to better protect the linear array of LED devices 102from degrading or burning by removing excess heat from the LED device102. The upper region 420 u (or the lower region 420 w), because it isspaced apart from the linear array of LED devices 102, plays a lesserrole than the horizontal middle region 420 hm in cooling the LED device102. The cost for making the LED filament 100 is thus economized whenthe upper region 420 u (or the lower region 420 w) is not as heavilydoped with nanoparticles as the horizontal middle region 420 hm. Thedimension of the horizontal middle region 420 hm, in which the lineararray of LED devices 102 is exclusively disposed, in relation to theentire enclosure 108 is determined by a desired totality ofconsiderations such as light conversion capability, bendability andthermal conductivity. Other things equal, the bigger the horizontalmiddle region 420 hm in relation to the entire enclosure 108, the LEDfilament 100 has greater light conversion capability and thermalconductivity but will be less bendable.

Staying on FIG. 27, the second set of hypothetical planes intersects theenclosure 108 parallelly to the light illuminating direction of thelinear array of LED devices 102. For example, the enclosure includesthree regions 274, 275, 276 defined by a hypothetical pair of planescompartmentalizing the enclosure 108 into a right region 420 r, a leftregion 420 l and a vertical middle region 420 vm sandwiched by the rightregion 420 r and the left region 420 l. The linear array of LED devices102 is disposed exclusively in one of the regions of the enclosure 108.Alternatively, the linear array of LED devices 102 is absent from atleast one of the regions of the enclosure 108. Alternatively, the lineararray of LED devices 102 is disposed in all regions of the enclosure108. In FIG. 27, the linear array of LED devices 102 is disposedexclusively in the vertical middle region 420 vm of the enclosure 108and is spaced apart by the vertical middle region 420 vm from the rightregion 420 r and the left region 420 l. In an embodiment, the verticalmiddle region 420 vm includes a wavelength converter for converting bluelight emitting from the LED device 102 into white light. The rightregion 420 r includes a cylindrical lens for aligning the light beamingrightwards. The left region 420 l includes a cylindrical lens foraligning the light beaming leftwards. In another embodiment, thevertical middle region 420 vm is made harder than the right region 420r, the left region 420 l or both by, for example, embedding a greaterconcentration of phosphor particles in the vertical middle region 420 vmthan in the right region 420 r, the left region 420 l or both. Thevertical middle region 420 vm, because it is harder, is thus configuredto better protect the linear array of LED devices 102 frommalfunctioning when the LED filament 100 is bent to maintain a desiredposture in a light bulb. The right region 420 r (or the left region 420l) is made softer for keeping the entire LED filament 100 as bendable inthe light bulb as it requires for generating omnidirectional light with,preferably, exactly one LED filament 100. In yet another embodiment, thevertical middle region 420 vm has greater thermal conductivity than theright region 420 r, the left region 420 l or both by, for example,doping a greater concentration of nanoparticles in the vertical middleregion 420 vm than in the right region 420 r, the left region 420 l orboth. The vertical middle region 420 vm, having greater thermalconductivity, is thus configured to better protect the linear array ofLED devices 102 from degrading or burning by removing excess heat fromthe LED device 102. The right region 420 r (or the left region 420 l),because it is spaced apart from the linear array of LED devices 102,plays a lesser role than the vertical middle region 420 vm in coolingthe LED device 102. The cost for making the LED filament 100 is thuseconomized when the right region 420 r (or the left region 420 l) is notas heavily doped with nanoparticles as the vertical middle region 420vm. The dimension of the vertical middle region 420 vm, in which thelinear array of LED devices 102 is exclusively disposed, in relation tothe entire enclosure 108 is determined by a desired totality ofconsiderations such as light conversion capability, bendability andthermal conductivity. Other things equal, the bigger the vertical middleregion 420 vm in relation to the entire enclosure 108, the LED filament100 has greater light conversion capability and thermal conductivity butwill be less bendable.

Still staying on FIG. 27, the third set of hypothetical planesintersects the enclosure 108 perpendicularly to the longitudinal axis ofthe enclosure 108. For example, the enclosure 108 includes twoalternating regions 420 f, 420 s, i.e. a first region 420 f and a secondregion 420 s, defined by the hypothetical set of parallel planes. In anembodiment, the hypothetical set of parallel planes intersect theenclosure 108 right at the edges of an LED device 102. The LED device102 is disposed exclusively in the first region 420 f. The means forelectrically connecting the LED devices 102, e.g. the bond wire, isdisposed exclusively in the second region 420 s. In another embodiment,the hypothetical set of parallel planes intersect the enclosure 108between the edges of an LED device 102. A portion of the LED device 102,excluding the edges, is disposed in the first region 420 f; the otherportion of the LED device 102, including the edges, is disposed in thesecond region 420 s. A portion of the means for electrically connectingthe LED devices 102, excluding the ends of the wiring, is disposed inthe second region 420 s; the other portion of the means for electricallyconnecting the LED devices 102, including the ends of the wiring, isdisposed in the second region 420 s. In yet another embodiment, thehypothetical set of parallel planes intersect the enclosure 108 at thespace between adjacent LED devices 102. The LED device 102 is disposedexclusively in the first region 420 f. A portion of the means forelectrically connecting the LED devices 102, excluding the ends of thewiring, is disposed in the first region 420 f; the other portion of themeans for electrically connecting the LED devices 102, including theends of the wiring, is disposed in the second region 420 s. Depending onapplications, the first region 420 f is configured to have a differentset of properties from that of the second region 420 s. In anembodiment, the first region 420 f is made harder than the second region420 s by, for example, embedding a greater concentration of phosphorparticles in the first region 420 f than in the second region 420 s. Thefirst region 420 f, because it is harder, is thus configured to betterprotect the linear array of LED devices 102 from malfunctioning when theLED filament 100 is bent to maintain a desired posture in a light bulb.The second region 420 s is made softer for keeping the entire LEDfilament 100 as bendable in the light bulb as it requires for generatingomnidirectional light with, preferably, exactly one LED filament 100. Inanother embodiment, the first region 420 f has greater thermalconductivity than the second region 420 s by, for example, doping agreater concentration of nanoparticles in the first region 420 f than inthe second region 420 s. The first region 420 f, having greater thermalconductivity, is thus configured to better protect the linear array ofLED devices 102 from degrading or burning by removing excess heat fromthe LED device 102. The second region 420 s, because it is spaced apartfrom the linear array of LED devices 102, plays a lesser role than thefirst region 420 f in cooling the LED device 102. The cost for makingthe LED filament 100 is thus economized when the second region 420 s isnot as heavily doped with nanoparticles as the first region 420 f Thedimension of the first region 420 f, in which the LED device 102 isdisposed, in relation to the entire enclosure 108 is determined by adesired totality of considerations such as light conversion capability,bendability and thermal conductivity. Other things equal, the bigger thefirst region 420 f in relation to the entire enclosure 108, the LEDfilament 100 has greater light conversion capability and thermalconductivity but will be less bendable.

Shifting to FIG. 28, the truncated LED filament 100 is further carvedinto a small portion and a big portion to show its internal structure.The small portion is defined by revolving the rectangle ABCD around theline CD (i.e. the central axis of the LED filament 100) for a fractionof 360 degrees. Likewise, the big portion is defined by revolving therectangle ABCD around the line CD for the entirety of 360 degrees exceptfor the space taken by the small portion. In an embodiment, theenclosure 108 is regionalized with, for example, a hypothetical set ofcylindrical surfaces in combination with a hypothetical set of planes.First, the regions 420 e, 420 m, 420 o of the enclosure 108 are definedby a hypothetical cylindrical surface having the longitudinal axis ofthe LED filament 100 as its central axis. For example, the enclosure 108includes three regions 420 e, 420 m, 420 o defined by a hypotheticalpair of coaxial cylindrical surfaces compartmentalizing the enclosure108 into a core region 420 e, an outer region 420 o and a tubular middleregion 420 m sandwiched by the core region 420 e and the outer region420 o. The linear array of LED devices 102 is disposed exclusively inone of the regions of the enclosure 108. Alternatively, the linear arrayof LED devices 102 is absent from at least one of the regions of theenclosure 108. Alternatively, the linear array of LED devices 102 isdisposed in all regions of the enclosure 108. In an embodiment, theouter region 420 o includes a light scatterer for increasing lightextraction from the LED device 102 by reducing total internalreflection. The tubular middle region 420 m includes a wavelengthconverter for converting blue light emitting from the LED device 102into white light. The core region 420 e includes a spacer. The spacerprevents heat coming from the LED device 102 from quickly degrading thephosphor particle by keeping the phosphor particle apart from the LEDdevice 102. Moreover, the spacer enables a uniform thickness for thetubular middle region 420 m, which includes the wavelength converter, toproduce uniform white light, which entails a proper combination of bluelight and the phosphor light. In another embodiment, the tubular middleregion 420 m is made harder than the core region 420 e, the outer region420 o or both by, for example, embedding a greater concentration ofphosphor particles in the tubular middle region 420 m than in the coreregion 420 e, the outer region 420 o or both. The tubular middle region420 m, because it is harder, is thus configured to better protect thelinear array of LED devices 102 from malfunctioning when the LEDfilament 100 is bent to maintain a desired posture in a light bulb. Thecore region 420 e (or the outer region 420 o) is made softer for keepingthe entire LED filament 100 as bendable in the light bulb as it requiresfor generating omnidirectional light with, preferably, exactly one LEDfilament 100. In yet another embodiment, the core region 420 e hasgreater thermal conductivity than the tubular middle region 420 m, theouter region 420 o or both by, for example, doping a greaterconcentration of nanoparticles in the core region 420 e than in thetubular middle region 420 m, the outer region 420 o or both. The coreregion 420 e, having greater thermal conductivity, is thus configured tobetter protect the linear array of LED devices 102 from degrading orburning by removing excess heat from the LED device 102. The tubularmiddle region 420 m (or the outer region 420 o), because it is spacedapart from the linear array of LED devices 102, plays a lesser role thanthe core region 420 e in cooling the LED device 102. The cost for makingthe LED filament 100 is thus economized when the tubular middle region420 m (or the outer region 420 o) is not as heavily doped withnanoparticles as the core region 420 e. The dimension of the core region420 e, in which the linear array of LED devices 102 is exclusivelydisposed, in relation to the entire enclosure 108 is determined by adesired totality of considerations such as light conversion capability,bendability and thermal conductivity. Other things equal, the bigger thecore region 420 e in relation to the entire enclosure 108, the LEDfilament 100 has less light conversion capability and thermalconductivity but will be more bendable. The dimension of the tubularmiddle region 420 m, which includes the wavelength converter, inrelation to the entire enclosure 108 is determined by a desired totalityof considerations such as light conversion capability, bendability andthermal conductivity. Other things equal, the bigger the middle region420 m in relation to the entire enclosure 108, the LED filament 100 hasgreater light conversion capability and thermal conductivity but will beless bendable. Next, the regions of the enclosure 108 are defined by ahypothetical set of parallel planes intersecting the enclosureperpendicularly to the longitudinal axis of the enclosure 108. Forexample, the enclosure 108 includes two alternating regions 420 f, 420s, i.e. a first region 420 f and a second region 420 s, defined by thehypothetical set of parallel planes. In an embodiment, the hypotheticalset of parallel planes intersect the enclosure 108 right at the edges ofan LED device 102. The LED device 102 is disposed exclusively in thefirst region 420 f. The means for electrically connecting the LEDdevices 102, e.g. the bond wire, is disposed exclusively in the secondregion 420 s. In another embodiment, the hypothetical set of parallelplanes intersect the enclosure 108 between the edges of an LED device102. A portion of the LED device 102, excluding the edges, is disposedin the first region 420 f; the other portion of the LED device 102,including the edges, is disposed in the second region 420 s. The meansfor electrically connecting the LED devices, including the ends of thewiring, is disposed in the second region 420 s. In yet anotherembodiment, the hypothetical set of parallel planes intersect theenclosure 108 at the space between adjacent LED devices 102. The LEDdevice 102 is disposed exclusively in the first region 420 f. A portionof the means for electrically connecting the LED devices 102, includingthe ends of the wiring, is disposed in the first region 420 f; the otherportion of the means for electrically connecting the LED devices 102,excluding the ends of the wiring, is disposed in the second region 420s. Depending on applications, the first region 420 f is configured tohave a different set of properties from that of the second region 420 s.In an embodiment, the first region 420 f is made harder than the secondregion 420 s by, for example, embedding a greater concentration ofphosphor particles in the first region 420 f than in the second region420 s. The first region 420 f, because it is harder, is thus configuredto better protect the linear array of LED devices 102 frommalfunctioning when the LED filament 100 is bent to maintain a desiredposture in a light bulb. The second region 420 s is made softer forkeeping the entire LED filament 100 as bendable in the light bulb as itrequires for generating omnidirectional light with, preferably, exactlyone LED filament 100. In another embodiment, the first region 420 f hasgreater thermal conductivity than the second region 420 s by, forexample, doping a greater concentration of nanoparticles in the firstregion 420 f than in the second region 420 s. The first region 420 f,having greater thermal conductivity, is thus configured to betterprotect the linear array of LED devices 102 from degrading or burning byremoving excess heat from the LED device 102. The second region 420 s,because it is spaced apart from the linear array of LED devices 102,plays a lesser role than the first region 420 f in cooling the LEDdevice 102. The cost for making the LED filament 100 is thus economizedwhen the second region 420 s is not as heavily doped with nanoparticlesas the first region 420 f The dimension of the first region 420 f, inwhich the LED device 102 is disposed, in relation to the entireenclosure 108 is determined by a desired totality of considerations suchas light conversion capability, bendability and thermal conductivity.Other things equal, the bigger the first region 420 f in relation to theentire enclosure 108, the LED filament 100 has greater light conversioncapability and thermal conductivity but will be less bendable.

The regions defined by the hypothetical set of cylindrical surfaces andthe hypothetical set of planes are either continuous or not continuous.Shifting to FIG. 29, the core region 420 e and the tubular middle region420 m extend longitudinally across the first region 420 f of theenclosure 108 but are broken periodically and absent from the secondregion 420 s. In other words, what would be a tubular middle region anda core region if the all regions were continuous in the second region420 s are merged into one region in the second region 420 s when allregions of the enclosure 108 are not continuous. For example, the outerregion 420 o, which is continuous throughout the enclosure 108, includesa light scatterer for reducing total internal reflection. The firstregion 420 f includes a tubular middle region 420 m and a core region420 e. The tubular middle region 420 m—sandwiched by the outer region420 o and the core region 420 e—includes a wavelength converter, e.g.phosphor particles embedded in a transparent binder, for producinguniform white light, which entails a proper combination of blue lightand the phosphor light. The core region 420 e includes a spacer forpreventing heat coming from the LED device 102 from degrading thephosphor particles in the wavelength converter prematurely. Moreover,the spacer enables a uniform thickness for the tubular middle region 420m. The second region 420 s, like the core region 420 e, also includes awavelength converter. In an embodiment, the second region 420 s issofter than the core region 420 e, the tubular middle region 420 m orboth such that the LED filament 100 is as bendable as it is required togenerate omnidirectional light with exactly one LED filament 100. Inanother embodiment, the second region 420 s is less thermally conductivethan the core region 420 e, the tubular middle region 420 m or both. Thecore region 420 e (or the tubular middle region 420 m) plays a biggerrole than the second region 420 s in removing heat generated by the LEDdevice 102.

In the embodiments where the enclosure is a modular structure assembledfrom modules having diverse chemical or physical properties, theenclosure includes a plurality of modules having distinctive propertiesto enable a desired totality of functions for the LED filament. Theplurality of modules in the enclosure is defined in a variety of waysdepending on applications. Going back to FIG. 23, the truncated LEDfilament 100 is further sliced vertically—i.e. along the lightilluminating direction of the linear array of LED devices 102—into equalhalves along the longitudinal axis of the LED filament 100 to show itsinternal structure. The modules of the enclosure 108 are defined by ahypothetical plane perpendicular to the light illuminating direction ofthe linear array of LED devices 102. For example, the enclosure 108includes three modules 420 w, 420 m, 420 u defined by a hypotheticalpair of planes compartmentalizing the enclosure 108 into an upper module420 u, a lower module 420 w and a middle module 420 m sandwiched by theupper module 420 u and the lower module 420 w. The linear array of LEDdevices 102 is disposed exclusively in one of the modules of theenclosure 108. Alternatively, the linear array of LED devices 102 isabsent from at least one of the modules of the enclosure 108.Alternatively, the linear array of LED devices 102 is disposed in allmodules of the enclosure 108. In FIG. 23, the linear array of LEDdevices 102 is disposed exclusively in the middle module 420 m of theenclosure 108 and is spaced apart by the middle module 420 m from thetop module 420 u and the lower module 420 w. In an embodiment, themiddle module 420 m includes a wavelength converter for converting bluelight emitting from the LED device 102 into white light. The uppermodule 420 u includes a cylindrical lens for aligning the light beamingupwards. The lower module 420 w includes a cylindrical lens for aligningthe light beaming downwards. In another embodiment, the middle module420 m is made harder than the upper module 420 u, the lower module 420 wor both by, for example, embedding a greater concentration of phosphorparticles in the middle module 420 m than in the upper module 420 u, thelower module 420 w or both. The middle module 420 m, because it isharder, is thus configured to better protect the linear array of LEDdevices 102 from malfunctioning when the LED filament 100 is bent tomaintain a desired posture in a light bulb. The upper module 420 u (orthe lower module 420 w) is made softer for keeping the entire LEDfilament 100 as bendable in the light bulb as it requires for generatingomnidirectional light with preferably exactly one LED filament 100. Inyet another embodiment, the middle module 420 m has greater thermalconductivity than the upper module 420 u, the lower module 420 w or bothby, for example, doping a greater concentration of nanoparticles in themiddle module 420 m than in the upper module 420 u, the lower module 420w or both. The middle module 420 m, having greater thermal conductivity,is thus configured to better protect the linear array of LED devices 102from degrading or burning by removing excess heat from the LED device102. The upper module 420 u (or the lower module 420 w), because it isspaced apart from the linear array of LED devices 102, plays a lesserrole than the middle module 420 m in cooling the LED device 102. Thecost for making the LED filament 100 is thus economized when the uppermodule 420 u (or the lower module 420 w) is not as heavily doped withnanoparticles as the middle module 420 m. The dimension of the middlemodule 420 m, in which the linear array of LED devices is exclusivelydisposed, in relation to the entire enclosure 108 is determined by adesired totality of considerations such as light conversion capability,bendability and thermal conductivity. Other things equal, the bigger themiddle module 420 m in relation to the entire enclosure 108, the LEDfilament 100 has greater light conversion capability and thermalconductivity but will be less bendable. A cross section perpendicular tothe longitudinal axis of the LED filament 100 reveals the middle module420 m and other modules of the enclosure 108. R6 is a ratio of the areaof the middle module 420 m to the overall area of the cross section.Preferably, R6 is from 0.2 to 0.8. Most preferably, R6 is from 0.4 to0.6.

Shifting to FIG. 24, the truncated LED filament 100 is further slicedhorizontally—i.e. perpendicular to the light illuminating direction ofthe linear array of LED devices 102—into equal halves along thelongitudinal axis of the LED filament 100 to show its internalstructure. The modules of the enclosure 108 are defined by ahypothetical plane parallel to the light illuminating direction of thelinear array of LED devices 102. For example, the enclosure 108 includesthree modules 420 l, 420 m, 420 r defined by a hypothetical pair ofplanes compartmentalizing the enclosure 108 into a right module 420 r, aleft module 420 l and a middle module 420 m sandwiched by the rightmodule 420 r and the left module 420 l. The linear array of LED devices102 is disposed exclusively in one of the modules of the enclosure 108.Alternatively, the linear array of LED devices 102 is absent from atleast one of the modules of the enclosure 108. Alternatively, the lineararray of LED devices 102 is disposed in all modules of the enclosure108. In FIG. 24, the linear array of LED devices 102 is disposedexclusively in the middle module 420 m of the enclosure 108 and isspaced apart by the middle module 420 m from the right module 420 r andthe left module 420 l. In an embodiment, the middle module 420 mincludes a wavelength converter for converting blue light emitting fromthe LED device 102 into white light. The right module 420 r includes acylindrical lens for aligning the light beaming rightwards. The leftmodule 420 l includes a cylindrical lens for aligning the light beamingleftwards. In another embodiment, the middle module 420 m is made harderthan the right module 420 r, the left module 420 l or both by, forexample, embedding a greater concentration of phosphor particles in themiddle module 420 m than in the right module 420 r, the left module 420l or both. The middle module 420 m, because it is harder, is thusconfigured to better protect the linear array of LED devices 102 frommalfunctioning when the LED filament 100 is bent to maintain a desiredposture in a light bulb. The right module 420 r (or the left module 420l) is made softer for keeping the entire LED filament 100 as bendable inthe light bulb as it requires for generating omnidirectional light with,preferably, exactly one LED filament 100. In yet another embodiment, themiddle module 420 m has greater thermal conductivity than the rightmodule 420 r, the left module 420 l or both by, for example, doping agreater concentration of nanoparticles in the middle module 420 m thanin the right module 420 r, the left module 420 l or both. The middlemodule 420 m, having greater thermal conductivity, is thus configured tobetter protect the linear array of LED devices 102 from degrading orburning by removing excess heat from the LED device 102. The rightmodule 420 r (or the left module 420 l), because it is spaced apart fromthe linear array of LED devices 102, plays a lesser role than the middlemodule 420 m in cooling the LED device 102. The cost for making the LEDfilament 100 is thus economized when the right module 420 r (or the leftmodule 420 l) is not as heavily doped with nanoparticles as the middlemodule 420 m. The dimension of the middle module 420 m, in which thelinear array of LED devices is exclusively disposed, in relation to theentire enclosure 108 is determined by a desired totality ofconsiderations such as light conversion capability, bendability andthermal conductivity. Other things equal, the bigger the middle module420 m in relation to the entire enclosure 108, the LED filament 100 hasgreater light conversion capability and thermal conductivity but will beless bendable. A cross section perpendicular to the longitudinal axis ofthe LED filament 100 reveals the middle module 420 m and other modulesof the enclosure 108. R7 is a ratio of the area of the middle module 420m to the overall area of the cross section. Preferably, R7 is from 0.2to 0.8. Most preferably, R7 is from 0.4 to 0.6.

Shifting to FIG. 25, the truncated LED filament 100 is further carvedinto a small portion and a big portion to show its internal structure.The small portion is defined by revolving the rectangle ABCD around theline CD (i.e. the central axis of the LED filament 100) for a fractionof 360 degrees. Likewise, the big portion is defined by revolving therectangle ABCD around the line CD but for the entirety of 360 degreesexcept for the space taken by the small portion. The modules of theenclosure 108 are defined by a hypothetical cylindrical surface havingthe central axis of the LED filament 100 as its central axis. Forexample, the enclosure 108 includes three modules 420 e, 420 m, 420 odefined by a hypothetical pair of coaxial cylindrical surfacescompartmentalizing the enclosure 108 into a core module 420 e, an outermodule 420 o and a middle module 420 m sandwiched by the core module 420e and the outer module 420 o. The linear array of LED devices 102 isdisposed exclusively in one of the modules of the enclosure 108.Alternatively, the linear array of LED devices 102 is absent from atleast one of the modules of the enclosure 108. Alternatively, the lineararray of LED devices 102 is disposed in all modules of the enclosure108. In FIG. 25, the linear array of LED devices 102 is disposedexclusively in the core module 420 e of the enclosure 108 and is spacedapart by the core module 420 e from the middle module 420 m and theouter module 420 o. In an embodiment, the outer module 420 o includes alight scatterer for increasing light extraction from the LED device 102by reducing total internal reflection. The middle module 420 m includesa wavelength converter for converting blue light emitting from the LEDdevice 102 into white light. The core module 420 e includes a spacer.The spacer prevents heat coming from the LED device 102 from quicklydegrading the phosphor particle by keeping the phosphor particle apartfrom the LED device 102. Moreover, the spacer enables a uniformthickness for the middle module 420 m, which includes the wavelengthconverter, to produce uniform white light, which entails a propercombination of blue light and the phosphor light. In another embodiment,the middle module 420 m is made harder than the core module 420 e, theouter module 420 o or both by, for example, embedding a greaterconcentration of phosphor particles in the middle module 420 m than inthe core module 420 e, the outer module 420 o or both. The middle module420 m, because it is harder, is thus configured to better protect thelinear array of LED devices 102 from malfunctioning when the LEDfilament 100 is bent to maintain a desired posture in a light bulb. Thecore module 420 e (or the outer module 420 o) is made softer for keepingthe entire LED filament 100 as bendable in the light bulb as it requiresfor generating omnidirectional light with, preferably, exactly one LEDfilament 100. In yet another embodiment, the core module 420 e hasgreater thermal conductivity than the middle module 420 m, the outermodule 420 o or both by, for example, doping a greater concentration ofnanoparticles in the core module 420 e than in the middle module 420 m,the outer module 420 o or both. The core module 420 e, having greaterthermal conductivity, is thus configured to better protect the lineararray of LED devices 102 from degrading or burning by removing excessheat from the LED device 102. The middle module 420 m (or the outermodule 420 o), because it is spaced apart from the linear array of LEDdevices 102, plays a lesser role than the core module 420 e in coolingthe LED device 102. The cost for making the LED filament 100 is thuseconomized when the middle module 420 m (or the outer module 420 o) isnot as heavily doped with nanoparticles as the core module 420 e. Thedimension of the core module 420 e, in which the linear array of LEDdevices 102 is exclusively disposed, in relation to the entire enclosure108 is determined by a desired totality of considerations such as lightconversion capability, bendability and thermal conductivity. Otherthings equal, the bigger the core module 420 e in relation to the entireenclosure 108, the LED filament 100 has less light conversion capabilityand thermal conductivity but will be more bendable. A cross sectionperpendicular to the longitudinal axis of the LED filament 100 revealsthe core module 420 e and other modules of the enclosure 108. R8 is aratio of the area of the core module 420 e to the overall area of thecross section. Preferably, R8 is from 0.1 to 0.8. Most preferably, R8 isfrom 0.2 to 0.5. The dimension of the middle module 420 m, whichincludes the wavelength converter, in relation to the entire enclosure108 is determined by a desired totality of considerations such as lightconversion capability, bendability and thermal conductivity. Otherthings equal, the bigger the middle module 420 m in relation to theentire enclosure 108, the LED filament 100 has greater light conversioncapability and thermal conductivity but will be less bendable. A crosssection perpendicular to the longitudinal axis of the LED filament 100reveals the middle module 420 m and other modules of the enclosure 108.R9 is a ratio of the area of the middle module 420 m to the overall areaof the cross section. Preferably, R9 is from 0.1 to 0.8. Mostpreferably, R9 is from 0.2 to 0.5.

Shifting to FIG. 26, the truncated LED filament 100 is further carvedinto a small portion and a big portion to show its internal structure.Like FIG. 25, the small portion is defined by revolving the rectangleABCD around the line CD (i.e. the central axis of the LED filament 100)for a fraction of 360 degrees. Likewise, the big portion is defined byrevolving the rectangle ABCD around the line CD for the entirety of 360degrees except for the space taken by the small portion. The modules ofthe enclosure 108 are defined by a hypothetical set of parallel planesintersecting the enclosure 108 perpendicularly to the longitudinal axisof the enclosure 108. For example, the enclosure 108 includes twoalternating modules 420 f, 420 s, i.e. a first module 420 f and a secondmodule 420 s, defined by the hypothetical set of parallel planes. In anembodiment, the hypothetical set of parallel planes intersect theenclosure 108 right at the edges of an LED device 102. The LED device102 is disposed exclusively in the first module 420 f. The means forelectrically connecting the LED devices 102, e.g. the bond wire, isdisposed exclusively in the second module 420 s. In another embodiment,the hypothetical set of parallel planes intersect the enclosure 108between the edges of an LED device 102. A portion of the LED device 102,excluding the edges, is disposed in the first module 420 f; the otherportion of the LED device 102, including the edges, is disposed in thesecond module 420 s. A portion of the means for electrically connectingthe LED devices 102, excluding the ends of the wiring, is disposed inthe second module 420 s; the other portion of the means for electricallyconnecting the LED devices 102, including the ends of the wiring, isdisposed in the first module 420 f. In yet another embodiment, thehypothetical set of parallel planes intersect the enclosure 108 at thespace between adjacent LED devices 102. The LED device 102 is disposedexclusively in the first module 420 f. A portion of the means forelectrically connecting the LED devices 102, including the ends of thewiring, is disposed in the first module 420 f; the other portion of themeans for electrically connecting the LED devices 102, excluding theends of the wiring, is disposed in the second module 420 s. Depending onapplications, the first module 420 f is configured to have a differentset of properties from that of the second module 420 s. In anembodiment, the first module 420 f is made harder than the second module420 s by, for example, embedding a greater concentration of phosphorparticles in the first module 420 f than in the second module 420 s. Thefirst module 420 f, because it is harder, is thus configured to betterprotect the linear array of LED devices 102 from malfunctioning when theLED filament 100 is bent to maintain a desired posture in a light bulb.The second module 420 s is made softer for keeping the entire LEDfilament 100 as bendable in the light bulb as it requires for generatingomnidirectional light with, preferably, exactly one LED filament 100. Inanother embodiment, the first module 420 f has greater thermalconductivity than the second module by, for example, doping a greaterconcentration of nanoparticles in the first module 420 f than in thesecond module 420 s. The first module 420 f, having greater thermalconductivity, is thus configured to better protect the linear array ofLED devices 102 from degrading or burning by removing excess heat fromthe LED device 102. The second module 420 s, because it is spaced apartfrom the linear array of LED devices 102, plays a lesser role than thefirst module 420 f in cooling the LED device 102. The cost for makingthe LED filament 100 is thus economized when the second module 420 s isnot as heavily doped with nanoparticles as the first module 420 f. Thedimension of the first module 420 f, in which the LED device 102 isdisposed, in relation to the entire enclosure 108 is determined by adesired totality of considerations such as light conversion capability,bendability and thermal conductivity. Other things equal, the bigger thefirst module 420 f in relation to the entire enclosure 108, the LEDfilament 100 has greater light conversion capability and thermalconductivity but will be less bendable. An outer surface of theenclosure 108 shows a combination of the first module 420 f and othermodules. R10 is a ratio of the total area of the first module 420 ffound on the outer surface to the overall area of the outer surface ofthe enclosure 108. Preferably, R10 is from 0.2 to 0.8. Most preferably,R10 is from 0.4 to 0.6.

The ways illustrated above in which an enclosure is divided into moduleshaving distinctive properties can be employed in combination with oneanother, in FIGS. 27 and 28 as examples, to functionalize an LEDfilament 100 as desired. In FIG. 27, the truncated LED filament 100 isfurther carved into a small portion and a big portion to show itsinternal structure. The small portion is defined by revolving therectangle ABCD around the line CD (i.e. the central axis of the LEDfilament 100) for 90 degrees. Likewise, the big portion is defined byrevolving the rectangle ABCD around the line CD for the entirety of 360degrees except for the space taken by the small portion. The enclosure108 is modularized with, for example, three sets of hypothetical planes.The first set of hypothetical planes intersect the enclosure 108perpendicularly to the light illuminating direction of the linear arrayof LED devices 102. For example, the enclosure 108 includes threemodules 420 u, 420 hm, 420 w defined by a hypothetical pair of planescompartmentalizing the enclosure 108 into an upper module 420 u, a lowermodule 420 w and a horizontal middle module 420 hm sandwiched by theupper module 420 u and the lower module 420 w. The linear array of LEDdevices 102 is disposed exclusively in one of the modules of theenclosure 108. Alternatively, the linear array of LED devices 102 isabsent from at least one of the modules of the enclosure 108.Alternatively, the linear array of LED devices 102 is disposed in allmodules of the enclosure 108. In FIG. 27, the linear array of LEDdevices 102 is disposed exclusively in the horizontal middle module 420hm of the enclosure 108 and is spaced apart by the horizontal middlemodule 420 hm from the top module 420 u and the lower module 420 l. Inan embodiment, the horizontal middle module 420 hm includes a wavelengthconverter for converting blue light emitting from the LED device 102into white light. The upper module 420 u includes a cylindrical lens foraligning the light beaming upwards. The lower module 420 l includes acylindrical lens for aligning the light beaming downwards. In anotherembodiment, the horizontal middle module 420 hm is made harder than theupper module 420 u, the lower module 420 l or both by, for example,embedding a greater concentration of phosphor particles in thehorizontal middle module 420 hm than in the upper module 420 u, thelower module 420 l or both. The horizontal middle module 420 hm, becauseit is harder, is thus configured to better protect the linear array ofLED devices 102 from malfunctioning when the LED filament 100 is bent tomaintain a desired posture in a light bulb. The upper module 420 u (orthe lower module 420 l) is made softer for keeping the entire LEDfilament 100 as bendable in the light bulb as it requires for generatingomnidirectional light with preferably exactly one LED filament 100. Inyet another embodiment, the horizontal middle module 420 hm has greaterthermal conductivity than the upper module 420 u, the lower module 420 lor both by, for example, doping a greater concentration of nanoparticlesin the horizontal middle module 420 hm than in the upper module 420 u,the lower module 420 l or both. The horizontal middle module 420 hm,having greater thermal conductivity, is thus configured to betterprotect the linear array of LED devices 102 from degrading or burning byremoving excess heat from the LED device 102. The upper module 420 u (orthe lower module 420 l), because it is spaced apart from the lineararray of LED devices 102, plays a lesser role than the horizontal middlemodule 420 hm in cooling the LED device 102. The cost for making the LEDfilament 100 is thus economized when the upper module 420 u (or thelower module 420 l) is not as heavily doped with nanoparticles as thehorizontal middle module 420 hm. The dimension of the horizontal middlemodule 420 hm, in which the linear array of LED devices 102 isexclusively disposed, in relation to the entire enclosure 108 isdetermined by a desired totality of considerations such as lightconversion capability, bendability and thermal conductivity. Otherthings equal, the bigger the horizontal middle module 420 hm in relationto the entire enclosure 108, the LED filament 100 has greater lightconversion capability and thermal conductivity but will be lessbendable.

Staying on FIG. 27, the second set of hypothetical planes, which areparallel to the central axis of the LED filament 100, intersect theenclosure 108 longitudinally. For example, the enclosure 108 includesthree modules 420 l, 420 vm, 420 r defined by a hypothetical pair ofplanes compartmentalizing the enclosure 108 into a right module 420 r, aleft module 420 l and a vertical middle module 420 vm sandwiched by theright module 420 r and the left module 420 l. The linear array of LEDdevices 102 is disposed exclusively in one of the modules of theenclosure 108. Alternatively, the linear array of LED devices 102 isabsent from at least one of the modules of the enclosure 108.Alternatively, the linear array of LED devices 102 is disposed in allmodules of the enclosure 108. In FIG. 27, the linear array of LEDdevices 102 is disposed exclusively in the vertical middle module 420 vmof the enclosure 108 and is spaced apart by the vertical middle module420 vm from the right module 420 r and the left module 420 l. In anembodiment, the vertical middle module 420 vm includes a wavelengthconverter for converting blue light emitting from the LED device 102into white light. The right module 420 r includes a cylindrical lens foraligning the light beaming rightwards. The left module 420 l includes acylindrical lens for aligning the light beaming leftwards. In anotherembodiment, the vertical middle module 420 vm is made harder than theright module 420 r, the left module 420 l or both by, for example,embedding a greater concentration of phosphor particles in the verticalmiddle module 420 vm than in the right module 420 r, the left module 420l or both. The vertical middle module 420 vm, because it is harder, isthus configured to better protect the linear array of LED devices 102from malfunctioning when the LED filament 100 is bent to maintain adesired posture in a light bulb. The right module 420 r (or the leftmodule 420 l) is made softer for keeping the entire LED filament 100 asbendable in the light bulb as it requires for generating omnidirectionallight with, preferably, exactly one LED filament 100. In yet anotherembodiment, the vertical middle module 420 vm has greater thermalconductivity than the right module 420 r, the left module 420 l or bothby, for example, doping a greater concentration of nanoparticles in thevertical middle module 420 vm than in the right module 420 r, the leftmodule 420 l or both. The vertical middle module 420 vm, having greaterthermal conductivity, is thus configured to better protect the lineararray of LED devices 102 from degrading or burning by removing excessheat from the LED device 102. The right module 420 r (or the left module420 l), because it is spaced apart from the linear array of LED devices102, plays a lesser role than the vertical middle module 420 vm incooling the LED device 102. The cost for making the LED filament 100 isthus economized when the right module 420 r (or the left module 420 l)is not as heavily doped with nanoparticles as the vertical middle module420 vm. The dimension of the vertical middle module 420 vm, in which thelinear array of LED devices 102 is exclusively disposed, in relation tothe entire enclosure 108 is determined by a desired totality ofconsiderations such as light conversion capability, bendability andthermal conductivity. Other things equal, the bigger the vertical middlemodule 420 vm in relation to the entire enclosure 108, the LED filament100 has greater light conversion capability and thermal conductivity butwill be less bendable.

The third set of hypothetical planes, which are perpendicular to thelongitudinal axis of the enclosure 108, intersect the enclosure 108radially. For example, the enclosure 108 includes two alternatingmodules 420 f, 420 s, i.e. a first module 420 f and a second module 420s, defined by the hypothetical set of parallel planes. In an embodiment,the hypothetical set of parallel planes intersect the enclosure 108right at the edges of an LED device 102. The LED device 102 is disposedexclusively in the first module 420 f. The means for electricallyconnecting the LED devices 102, e.g. the bond wire, is disposedexclusively in the second module 420 s. In another embodiment, thehypothetical set of parallel planes intersect the enclosure 108 betweenthe edges of an LED device 102. A portion of the LED device 102,excluding the edges, is disposed in the first module 420 f; the otherportion of the LED device, including the edges, is disposed in thesecond module 420 s. A portion of the means for electrically connectingthe LED devices 102, excluding the ends of the wiring, is disposed inthe second module 420 s; the other portion of the means for electricallyconnecting the LED devices, including the ends of the wiring, isdisposed in the first module 420 f. In yet another embodiment, thehypothetical set of parallel planes intersect the enclosure 108 at thespace between adjacent LED devices 102. The LED device 102 is disposedexclusively in the first module 420 f. A portion of the means forelectrically connecting the LED devices 102, excluding the ends of thewiring, is disposed in the second module 420 s; the other portion of themeans for electrically connecting the LED devices 102, including theends of the wiring, is disposed in the first module 420 f. Depending onapplications, the first module 420 f is configured to have a differentset of properties from that of the second module 420 s. In anembodiment, the first module 420 f is made harder than the second module420 s by, for example, embedding a greater concentration of phosphorparticles in the first module 420 f than in the second module 420 s. Thefirst module 420 f, because it is harder, is thus configured to betterprotect the linear array of LED devices 102 from malfunctioning when theLED filament 100 is bent to maintain a desired posture in a light bulb.The second module 420 s is made softer for keeping the entire LEDfilament 100 as bendable in the light bulb as it requires for generatingomnidirectional light with, preferably, exactly one LED filament 100. Inanother embodiment, the first module 420 f has greater thermalconductivity than the second module 420 s by, for example, doping agreater concentration of nanoparticles in the first module 420 f than inthe second module 420 s. The first module 420 f, having greater thermalconductivity, is thus configured to better protect the linear array ofLED devices 102 from degrading or burning by removing excess heat fromthe LED device 102. The second module 420 s, because it is spaced apartfrom the linear array of LED devices 102, plays a lesser role than thefirst module 420 f in cooling the LED device 102. The cost for makingthe LED filament 100 is thus economized when the second module 420 s isnot as heavily doped with nanoparticles as the first module 420 f. Thedimension of the first module 420 f, in which the LED device 102 isdisposed, in relation to the entire enclosure 108 is determined by adesired totality of considerations such as light conversion capability,bendability and thermal conductivity. Other things equal, the bigger thefirst module 420 f in relation to the entire enclosure 108, the LEDfilament 100 has greater light conversion capability and thermalconductivity but will be less bendable.

Shifting to FIG. 28, the truncated LED filament 100 is further carvedinto a small portion and a big portion to show its internal structure.The small portion is defined by revolving the rectangle ABCD around theline CD (i.e. the longitudinal axis of the LED filament 100) for afraction of 360 degrees. Likewise, the big portion is defined byrevolving the rectangle ABCD around the line CD for the entirety of 360degrees except for the space taken by the small portion. In anembodiment, the enclosure 108 is modularized with, for example, ahypothetical set of cylindrical surfaces in combination with ahypothetical set of planes. First, the modules of the enclosure 108 aredefined by a set of hypothetical cylindrical surfaces having thelongitudinal axis of the LED filament 100 as their central axis. Forexample, the enclosure 108 includes three modules 420 e, 420 m, 420 odefined by a hypothetical pair of coaxial cylindrical surfacescompartmentalizing the enclosure 108 into a core module 420 e, an outermodule 420 o and a tubular middle module 420 m sandwiched by the coremodule 420 e and the outer module 420 o. The linear array of LED devices102 is disposed exclusively in one of the modules of the enclosure 108.Alternatively, the linear array of LED devices 102 is absent from atleast one of the modules of the enclosure 108. Alternatively, the lineararray of LED devices 102 is disposed in all modules of the enclosure108. In an embodiment, the outer module 420 o includes a light scattererfor increasing light extraction from the LED device 102 by reducingtotal internal reflection. The tubular middle module 420 m includes awavelength converter for converting blue light emitting from the LEDdevice 102 into white light. The core module 420 e includes a spacer.The spacer prevents heat coming from the LED device 102 from quicklydegrading the phosphor particle by keeping the phosphor particle apartfrom the LED device 102. Moreover, the spacer enables a uniformthickness for the tubular middle module 420 m, which includes thewavelength converter, to produce uniform white light, which entails aproper combination of blue light and the phosphor light. In anotherembodiment, the tubular middle module 420 m is made harder than the coremodule 420 e, the outer module 420 o or both by, for example, embeddinga greater concentration of phosphor particles in the tubular middlemodule 420 m than in the core module 420 e, the outer module 420 o orboth. The tubular middle module 420 m, because it is harder, is thusconfigured to better protect the linear array of LED devices 102 frommalfunctioning when the LED filament 100 is bent to maintain a desiredposture in a light bulb. The core module 420 e (or the outer module 420o) is made softer for keeping the entire LED filament 100 as bendable inthe light bulb as it requires for generating omnidirectional light with,preferably, exactly one LED filament 100. In yet another embodiment, thecore module 420 e has greater thermal conductivity than the tubularmiddle module 420 m, the outer module 420 o or both by, for example,doping a greater concentration of nanoparticles in the core module 420 ethan in the tubular middle module 420 m, the outer module 420 o or both.The core module 420 e, having greater thermal conductivity, is thusconfigured to better protect the linear array of LED devices 102 fromdegrading or burning by removing excess heat from the LED device 102.The tubular middle module 420 m (or the outer module 420 o), because itis spaced apart from the linear array of LED devices 102, plays a lesserrole than the core module 420 e in cooling the LED device 102. The costfor making the LED filament 100 is thus economized when the tubularmiddle module 420 m (or the outer module 420 o) is not as heavily dopedwith nanoparticles as the core module 420 e. The dimension of the coremodule 420 e, in which the linear array of LED devices 102 isexclusively disposed, in relation to the entire enclosure 108 isdetermined by a desired totality of considerations such as lightconversion capability, bendability and thermal conductivity. Otherthings equal, the bigger the core module 420 e in relation to the entireenclosure 108, the LED filament 100 has less light conversion capabilityand thermal conductivity but will be more bendable. The dimension of thetubular middle module 102, which includes the wavelength converter, inrelation to the entire enclosure 108 is determined by a desired totalityof considerations such as light conversion capability, bendability andthermal conductivity. Other things equal, the bigger the tubular middlemodule 420 m in relation to the entire enclosure 108, the LED filament100 has greater light conversion capability and thermal conductivity butwill be less bendable. Next, the modules of the enclosure 108 aredefined by a hypothetical set of parallel planes, which areperpendicular to the longitudinal axis of the enclosure 108 andintersect the enclosure 108 radially. For example, the enclosure 108includes two alternating modules 420 f, 420 s, i.e. a first module 420 fand a second module 420 s, defined by the hypothetical set of parallelplanes. In an embodiment, the hypothetical set of parallel planesintersect the enclosure 108 right at the edges of an LED device 102. TheLED device 102 is disposed exclusively in the first module 420 f. Themeans for electrically connecting the LED devices 102, e.g. the bondwire, is disposed exclusively in the second module 420 s. In anotherembodiment, the hypothetical set of parallel planes intersect theenclosure 108 between the edges of an LED device 102. A portion of theLED device 102, excluding the edges, is disposed in the first module 420f; the other portion of the LED device 102, including the edges, isdisposed in the second module 420 s. A portion of the means forelectrically connecting the LED devices 102, excluding the ends of thewiring, is disposed in the second module 420 s; the other portion of themeans for electrically connecting the LED devices 102, including theends of the wiring, is disposed in the first module 420 f. In yetanother embodiment, the hypothetical set of parallel planes intersectthe enclosure 108 at the space between adjacent LED devices 102. The LEDdevice 102 is disposed exclusively in the first module 420 f. A portionof the means for electrically connecting the LED devices 102, includingthe ends of the wiring, is disposed in the first module 420 f; the otherportion of the means for electrically connecting the LED devices 102,excluding the ends of the wiring, is disposed in the second module 420s. Depending on applications, the first module 420 f is configured tohave a different set of properties from that of the second module 420 s.In an embodiment, the first module 420 f is made harder than the secondmodule 420 s by, for example, embedding a greater concentration ofphosphor particles in the first module 420 f than in the second module420 s. The first module 420 f, because it is harder, is thus configuredto better protect the linear array of LED devices 102 frommalfunctioning when the LED filament 100 is bent to maintain a desiredposture in a light bulb. The second module 420 s is made softer forkeeping the entire LED filament 100 as bendable in the light bulb as itrequires for generating omnidirectional light with, preferably, exactlyone LED filament 100. In another embodiment, the first module 420 f hasgreater thermal conductivity than the second module 420 s by, forexample, doping a greater concentration of nanoparticles in the firstmodule 420 f than in the second module 420 s. The first module 420 f,having greater thermal conductivity, is thus configured to betterprotect the linear array of LED devices 102 from degrading or burning byremoving excess heat from the LED device 102. The second module 420 s,because it is spaced apart from the linear array of LED devices 102,plays a lesser role than the first module 420 f in cooling the LEDdevice 102. The cost for making the LED filament 100 is thus economizedwhen the second module 420 s is not as heavily doped with nanoparticlesas the first module 420 f. The dimension of the first module 420 f, inwhich the LED device 102 is disposed, in relation to the entireenclosure 108 is determined by a desired totality of considerations suchas light conversion capability, bendability and thermal conductivity.Other things equal, the bigger the first module 420 f in relation to theentire enclosure 108, the LED filament 100 has greater light conversioncapability and thermal conductivity but will be less bendable.

The modules defined by the hypothetical set of cylindrical surfaces andthe hypothetical set of planes are either continuous or not continuous.Shifting to FIG. 29, the core module 420 e and the tubular middle module420 m extend longitudinally across the first module 420 f of theenclosure 108 but are broken periodically and absent from the secondmodule 420 s. In other words, what would be a tubular middle module anda core module if the all modules were continuous in the second module420 s are merged into one module in the second module 420 s when allmodules of the enclosure 108 are not continuous. For example, the outermodule 420 o, which is continuous throughout the enclosure 108, includesa light scatterer for reducing total internal reflection. The firstmodule 420 f includes a tubular middle module 420 m and a core module420 e. The tubular middle module 420 m—sandwiched by the outer module420 o and the core module 420 e—includes a wavelength converter, e.g.phosphor particles embedded in a transparent binder, for producinguniform white light, which entails a proper combination of blue lightand the phosphor light. The core module 420 e includes a spacer forpreventing heat coming from the LED device 102 from degrading thephosphor particles in the wavelength converter prematurely. Moreover,the spacer enables a uniform thickness for the tubular middle region 420m. The second module 420 s, like the tubular middle module 420 m, alsoincludes a wavelength converter. In an embodiment, the second module 420s is softer than the core module 420 e, the tubular middle module 420 mor both such that the LED filament 100 is as bendable as it is requiredto generate omnidirectional light with exactly one LED filament 100. Inanother embodiment, the second module 420 s is less thermally conductivethan the core module 420 e, the tubular middle module 420 m or both. Thecore module 420 e (or the tubular middle module 420 m) plays a biggerrole than the second module 420 s in removing heat generated by the LEDdevice 102.

The LED filament of the present invention is configured to withstandbending and stay operable under the working temperature of the LEDdevice. Thus, when an enclosure includes a plurality of modules, theplurality of modules are configured to interconnect durably and form aunitary structure. In an embodiment, the interface that interconnectsthe plurality of modules is provided by a suitable glue that fills upthe gaps between the surfaces of adjacent modules. In anotherembodiment, the module includes a coarse surface for strengthening thefriction between adjacent modules. In yet another embodiment, theplurality of modules are connected with an interlocker, which includes amale structure and a female structure. FIGS. 30 to 32 show a truncatedLED filament 100 in accordance with an exemplary embodiment of thepresent invention. The enclosure 108 includes a first module 1081 and asecond module 1082. In FIG. 30, the linear array of LED devices 102 isdisposed in the first module 1081. The first module 1081 includes afemale structure for interlocking with the second module 1082 having amale structure. In FIG. 31, the linear array of LED devices 102 isdisposed in the second module 1082. The first module 1081 includes afemale structure for interlocking with the second module 1082 having amale structure. In FIG. 32, the linear array of LED devices 102 isdisposed in the first module 1081. Both of the first module 1081 and thesecond module 1082 include a male structure and a female structure forinterlocking the first module 1081 and the second module 1082. Relatedfeatures may be referred to FIG. 49H to FIG. 49K in application of U.S.Ser. No. 15/499,143 filed Apr. 27, 2017.

Where the enclosure is a modular structure assembled from modules havingdiverse chemical or physical properties, the enclosure includes aplurality of modules having distinctive properties to enable a desiredtotality of functions for the LED filament. In some embodiments, amodule in the enclosure has a uniform set of properties throughout themodule. In other embodiments, the enclosure further includes amulti-functional module. The multi-functional module, thoughstructurally indivisible, is functionally divisible into a plurality ofregions having distinctive sets of properties in different regions. Theplurality of modules in the enclosure and the plurality of regions inthe multi-functional module can be defined in a variety of waysdepending on applications. Going back to FIG. 23, the truncated LEDfilament 100 is further sliced vertically—i.e. along the lightilluminating direction of the linear array of LED devices 102—into equalhalves along the longitudinal axis of the LED filament 100 to show itsinternal structure. The modules 420 u, 420 g 1 of the enclosure 108 andthe regions 420 w, 420 m of the multi-functional module 420 g 1 aredefined by a hypothetical plane perpendicular to the light illuminatingdirection of the linear array of LED devices 102. For example, theenclosure 108 includes two modules defined by a hypothetical pair ofplanes compartmentalizing the enclosure 108 into an upper module 420 uand a multi-functional module 420 g 1 having a lower region 420 w and amiddle region 420 m sandwiched by the upper module 420 u and the lowerregion 420 w. The linear array of LED devices 102 is disposedexclusively in one of the modules of the enclosure 108. Alternatively,the linear array of LED devices 102 is absent from at least one of themodules of the enclosure 108. Alternatively, the linear array of LEDdevices 102 is disposed in all modules of the enclosure 108. When atleast a portion of the linear array of LED devices 102 is found in themulti-functional module 420 g 1, the potion of the linear array of LEDdevices 102 is disposed exclusively in one of the regions of themulti-functional module 420 g 1. Alternatively, the portion of thelinear array of LED devices 102 is absent from at least one of theregions of the multi-functional module 420 g 1. Alternatively, theportion of the linear array of LED devices 102 is disposed in allregions of the multi-functional module 420 g 1. Staying on FIG. 23, thelinear array of LED devices 102 is disposed exclusively in the middleregion 420 m of the multi-functional module 420 g 1 and is spaced apartby the middle region 420 m of the multi-functional module 420 g 1 fromthe top module 420 u and the lower region 420 w of the multi-functionalmodule 420 g 1. In an embodiment, the middle region 420 m ofmulti-functional module 420 g 1 includes a wavelength converter forconverting blue light emitting from the LED device 102 into white light.The upper module 420 u includes a cylindrical lens for aligning thelight beaming upwards. The lower region 420 w of the multi-functionalmodule 420 g 1 includes a cylindrical lens for aligning the lightbeaming downwards. In another embodiment, the middle region 420 m of themulti-functional module 420 g 1 is made harder than the upper module 420u, the lower region 420 w of the multi-functional module 420 g 1 or bothby, for example, embedding a greater concentration of phosphor particlesin the middle region 420 m of the multi-functional module 420 g 1 thanin the upper module 420 u, the lower region 420 w of themulti-functional module 420 g 1 or both. The middle region 420 m of themulti-functional module 420 g 1, because it is harder, is thusconfigured to better protect the linear array of LED devices 102 frommalfunctioning when the LED filament 100 is bent to maintain a desiredposture in a light bulb. The upper module 420 u (or the lower region 420w of the multi-functional module 420 g 1) is made softer for keeping theentire LED filament 100 as bendable in the light bulb as it requires forgenerating omnidirectional light with preferably exactly one LEDfilament 100. In yet another embodiment, the middle region 420 m of themulti-functional module 420 g 1 has greater thermal conductivity thanthe upper module 420 u, the lower region 420 w of the multi-functionalmodule 420 g 1 or both by, for example, doping a greater concentrationof nanoparticles in the middle region 420 m of the multi-functionalmodule 420 g 1 than the upper module 420 u, the lower region 420 w ofthe multi-functional module 420 g 1 or both. The middle region 420 m ofthe multi-functional module 420 g 1, having greater thermalconductivity, is thus configured to better protect the linear array ofLED devices 102 from degrading or burning by removing excess heat fromthe LED device 102. The upper module 420 u (or the lower region 420 w ofthe multi-functional module 420 g 1), because it is spaced apart fromthe linear array of LED devices 102, plays a lesser role than the middleregion 420 m of the multi-functional module 420 g 1 in cooling the LEDdevice 102. The cost for making the LED filament 100 is thus economizedwhen the upper module 420 u (or the lower region 420 w of themulti-functional module) is not as heavily doped with nanoparticles asthe middle region 420 m of the multi-functional module 420 g 1. Thedimension of the middle region 420 m of the multi-functional module 420g 1, in which the linear array of LED devices 102 is exclusivelydisposed, in relation to the entire enclosure 108 is determined by adesired totality of considerations such as light conversion capability,bendability and thermal conductivity. Other things equal, the bigger themiddle region 420 m of the multi-functional module 420 g 1 in relationto the entire enclosure 108, the LED filament 100 has greater lightconversion capability and thermal conductivity but will be lessbendable. A cross section of the enclosure 108 perpendicular to thelongitudinal axis of the LED filament 100 reveals the middle region 420m of the multi-functional module 420 g 1 and other modules of theenclosure 108. R11 is a ratio of the area of the middle region 420 m ofthe multi-functional module 420 g 1 to the overall area of the crosssection of the enclosure 108. Preferably, R11 is from 0.2 to 0.8. Mostpreferably, R11 is from 0.4 to 0.6.

Shifting to FIG. 24, the truncated LED filament 100 is further slicedhorizontally—i.e. perpendicular to the light illuminating direction ofthe linear array of LED devices 102—into equal halves along thelongitudinal axis of the LED filament 100 in order to show its internalstructure. The modules 420 r, 420 g 2 of the enclosure 108 and theregions 420 l, 420 m of the multi-functional module 420 g 2 are definedby a hypothetical plane parallel to the light illuminating direction ofthe linear array of LED devices 102. For example, the enclosure 108includes two modules 420 r, 420 g 2 defined by a hypothetical pair ofplanes compartmentalizing the enclosure 108 into a right module 420 rand a multi-functional module 420 g 2 having a left region 420 l and amiddle region 420 m sandwiched by the right module 420 r and the leftregion 420 l of the multi-functional module 420 g 2. The linear array ofLED devices 102 is disposed exclusively in one of the modules of theenclosure 108. Alternatively, the linear array of LED devices 102 isabsent from at least one of the modules of the enclosure 108.Alternatively, the linear array of LED devices 102 is disposed in allmodules of the enclosure 108. When at least a portion of the lineararray of LED devices 102 is found in the multi-functional module 420 g2, the portion of the linear array of LED devices 102 is disposedexclusively in one of the regions of the multi-functional module 420 g2. Alternatively, the portion of the linear array of LED devices 102 isabsent from at least one of the regions of the multi-functional module420 g 2. Alternatively, the portion of the linear array of LED devices420 g 2 is disposed in all regions of the multi-functional module 420 g2. Staying on FIG. 24, the linear array of LED devices 102 is disposedexclusively in the middle region 420 m of the multi-functional module420 g 2 and is spaced apart by the middle region 420 m of themulti-functional module 420 g 2 from the right module 420 r and the leftregion 420 l of the multi-functional module 420 g 2. In an embodiment,the middle region 420 m of the multi-functional module 420 g 2 includesa wavelength converter for converting blue light emitting from the LEDdevice 102 into white light. The right module 420 r includes acylindrical lens for aligning the light beaming rightwards. The leftregion 420 l of the multi-functional module 243 includes a cylindricallens for aligning the light beaming leftwards. In another embodiment,the middle region 420 m of the multi-functional module 240 g 2 is madeharder than the right module 420 r, the left region 420 l of themulti-functional module 420 g 2 or both by, for example, embedding agreater concentration of phosphor particles in the middle region 420 mof the multi-functional module 420 g 2 than in the right module 420 r,the left region 420 l of the multi-functional module 420 g 2 or both.The middle region 420 m of the multi-functional module 420 g 2, becauseit is harder, is thus configured to better protect the linear array ofLED devices 102 from malfunctioning when the LED filament 100 is bent tomaintain a desired posture in a light bulb. The right module 420 r (orthe left region 420 l of the multi-functional module 420 g 2) is madesofter for keeping the entire LED filament 100 as bendable in the lightbulb as it requires for generating omnidirectional light with,preferably, exactly one LED filament 100. In yet another embodiment, themiddle region 420 m of the multi-functional module 420 g 2 has greaterthermal conductivity than the right module 420 r, the left region 420 lof the multi-functional module 420 g 2 or both by, for example, doping agreater concentration of nanoparticles in the middle region 420 m of themulti-functional module 420 g 2 than in the right module 420 r, the leftregion 420 l of the multi-functional module 420 g 2 or both. The middleregion 420 m of the multi-functional module 420 g 2, having greaterthermal conductivity, is thus configured to better protect the lineararray of LED devices 102 from degrading or burning by removing excessheat from the LED device 102. The right module 420 r (or the left region420 l of the multi-functional module 420 g 2), because it is spacedapart from the linear array of LED devices 102, plays a lesser role thanthe middle region 420 m of the multi-functional module 420 g 2 incooling the LED device 102. The cost for making the LED filament 100 isthus economized when the right module 420 r (or the left region 420 l ofthe multi-functional module 420 g 2) is not as heavily doped withnanoparticles as the middle region 420 m of the multi-functional module420 g 2. The dimension of the middle region 420 m of themulti-functional module 420 g 2, in which the linear array of LEDdevices 102 is exclusively disposed, in relation to the entire enclosure108 is determined by a desired totality of considerations such as lightconversion capability, bendability and thermal conductivity. Otherthings equal, the bigger the middle region 420 m of the multi-functionalmodule 420 g 2 in relation to the entire enclosure 108, the LED filament100 has greater light conversion capability and thermal conductivity butwill be less bendable. A cross section of the enclosure 108perpendicular to the longitudinal axis of the LED filament 100 revealsthe middle region 420 m of the multi-functional module 420 g 2 and othermodules of the enclosure 108. R12 is a ratio of the area of the middleregion 420 m of the multi-functional module 420 g 2 to the overall areaof the cross section of the enclosure 108. Preferably, R12 is from 0.2to 0.8. Most preferably, R12 is from 0.4 to 0.6.

Shifting to FIG. 25, the truncated LED filament 100 is further carvedinto a small portion and a big portion to show its internal structure.The small portion is defined by revolving the rectangle ABCD around theline CD (i.e. the central axis of the LED filament 100) for a fractionof 360 degrees. Likewise, the big portion is defined by revolving therectangle ABCD around the line CD for the entirety of 360 degrees exceptfor the space taken by the small portion. The modules 420 e, 420 g 3 ofthe enclosure 108 and the regions 420 m, 420 o of the multi-functionalmodule 420 g 3 are defined by a hypothetical cylindrical surface havingthe central axis of the LED filament 100 as its central axis. Forexample, the enclosure 108 includes two modules 420 e, 420 g 3 definedby a hypothetical pair of coaxial cylindrical surfacescompartmentalizing the enclosure 108 into a core module 420 e, amulti-functional module 420 g 3 having an outer region 420 o and amiddle region 420 m sandwiched by the core module 420 e and the outerregion 420 o of the multi-functional module 420 g 3. The linear array ofLED devices 102 is disposed exclusively in one of the modules of theenclosure 108. Alternatively, the linear array of LED devices 102 isabsent from at least one of the modules of the enclosure 108.Alternatively, the linear array of LED devices 102 is disposed in allmodules of the enclosure 108. When at least a portion of the lineararray of LED devices 102 is found in the multi-functional module 420 g3, the potion of the linear array of LED devices 102 is disposedexclusively in one of the regions of the multi-functional module 420 g3. Alternatively, the portion of the linear array of LED devices 102 isabsent from at least one of the regions of the multi-functional module420 g 3. Alternatively, the portion of the linear array of LED devices102 is disposed in all regions of the multi-functional module 420 g 3.Staying on FIG. 25, the linear array of LED devices 102 is disposedexclusively in the core module 420 e of the enclosure 108 and is spacedapart by the core module 420 e from the middle region 420 m of themulti-functional module 420 g 3 and the outer region 420 o of themulti-functional module 420 g 3. In an embodiment, the outer region 420o of the multi-functional module 420 g 3 includes a light scatterer forincreasing light extraction from the LED device 102 by reducing totalinternal reflection. The middle region 420 m of the multi-functionalmodule 420 e includes a wavelength converter for converting blue lightemitting from the LED device 102 into white light. The core module 420 eincludes a spacer. The spacer prevents heat coming from the LED device102 from quickly degrading the phosphor particle by keeping the phosphorparticle apart from the LED device 102. Moreover, the spacer enables auniform thickness for the middle region 420 m of the multi-functionalmodule 420 g 3, which includes the wavelength converter, to produceuniform white light, which entails a proper combination of blue lightand the phosphor light. In another embodiment, the middle region 420 mof the multi-functional module 420 g 3 is made harder than the coremodule 420 e, the outer region 420 o of the multi-functional module 420g 3 or both by, for example, embedding a greater concentration ofphosphor particles in the middle region 420 m of the multi-functionalmodule 420 g 3 than in the core module 420 e, the outer region 420 o ofthe multi-functional module 420 g 3 or both. The middle region 420 m ofthe multi-functional module 420 g 3, because it is harder, is thusconfigured to better protect the linear array of LED devices 102 frommalfunctioning when the LED filament 100 is bent to maintain a desiredposture in a light bulb. The core module 420 e (or the outer region 420o of the multi-functional module 420 g 3) is made softer for keeping theentire LED filament 100 as bendable in the light bulb as it requires forgenerating omnidirectional light with, preferably, exactly one LEDfilament 100. In yet another embodiment, the core module 420 e hasgreater thermal conductivity than the middle region 420 m of themulti-functional module 420 g 3, the outer region 420 o of themulti-functional module 420 g 3 or both by, for example, doping agreater concentration of nanoparticles in the core module 420 e than inthe middle region 420 m of the multi-functional module 420 g 3, theouter region 420 o of the multi-functional module 420 g 3 or both. Thecore module 420 e, having greater thermal conductivity, is thusconfigured to better protect the linear array of LED devices 102 fromdegrading or burning by removing excess heat from the LED device 102.The middle region 420 m of the multi-functional module 420 g 3 (or theouter region 420 o of the multi-functional module 420 g 3), because itis spaced apart from the linear array of LED devices 102, plays a lesserrole than the core module 420 e in cooling the LED device 102. The costfor making the LED filament 100 is thus economized when the middleregion 420 m of the multi-functional module 420 g 3 (or the outer region420 o of the multi-functional module 420 g 3) is not as heavily dopedwith nanoparticles as the core module 420 e. The dimension of the coremodule 420 e, in which the linear array of LED devices 102 isexclusively disposed, in relation to the entire enclosure 108 isdetermined by a desired totality of considerations such as lightconversion capability, bendability and thermal conductivity. Otherthings equal, the bigger the core module 420 e in relation to the entireenclosure 108, the LED filament 100 has less light conversion capabilityand thermal conductivity but will be more bendable. A cross section ofthe enclosure 108 perpendicular to the longitudinal axis of the LEDfilament 100 reveals the core module 420 e and other modules of theenclosure 108. R13 is a ratio of the area of the core module 420 e tothe overall area of the cross section of the enclosure 108. Preferably,R13 is from 0.1 to 0.8. Most preferably, R13 is from 0.2 to 0.5. Thedimension of the middle region 420 m of the multi-functional module 420g 3, which includes the wavelength converter, in relation to the entireenclosure 108 is determined by a desired totality of considerations suchas light conversion capability, bendability and thermal conductivity.Other things equal, the bigger the middle region 420 m of themulti-functional module 420 g 3 in relation to the entire enclosure 108,the LED filament 100 has greater light conversion capability and thermalconductivity but will be less bendable. A cross section of the enclosure108 perpendicular to the longitudinal axis of the LED filament 100reveals the middle region 420 m of the multi-functional module 420 g 3and other portions of the enclosure 108. R14 is a ratio of the area ofthe middle region 420 m of the multi-functional module 420 g 3 to theoverall area of the cross section of the enclosure 108. Preferably, R14is from 0.1 to 0.8. Most preferably, R14 is from 0.2 to 0.5.

Shifting to FIG. 26, the truncated LED filament 100 is further carvedinto a small portion and a big portion to show its internal structure.Like FIG. 25, the small portion is defined by revolving the rectangleABCD around the line CD (i.e. the central axis of the LED filament 100)for a fraction of 360 degrees. Likewise, the big portion is defined byrevolving the rectangle ABCD around the line CD for the entirety of 360degrees except for the space taken by the small portion. The modules ofthe enclosure 108 and the regions of the multi-functional module aredefined by a hypothetical set of parallel planes intersecting theenclosure 108 perpendicularly to the longitudinal axis of the enclosure108. For example, the enclosure 108 includes a plurality of seriallyconnected multi-functional modules 420 g 4. The multi-functional module420 g 4 includes a first region 420 f and a second region 420 s. Thepair of alternating regions 420 f, 420 s in the enclosure 108, i.e. afirst region 420 f and a second region 420 s, are defined by ahypothetical set of parallel planes. In an embodiment, the hypotheticalset of parallel planes intersect the enclosure 108 right at the edges ofan LED device 102. The LED device 102 is disposed exclusively in thefirst region 420 f of the multi-functional module 420 g 4. The means forelectrically connecting the LED devices 102, e.g. the bond wire, isdisposed exclusively in the second region 420 s of the multi-functionalmodule 420 g 4. In another embodiment, the hypothetical set of parallelplanes intersect the enclosure 108 between the edges of an LED device102. A portion of the LED device 102, excluding the edges, is disposedin the first region 420 f of the multi-functional module 420 g 4; theother portion of the LED device 102, including the edges, is disposed inthe second region 420 s of the multi-functional module 420 g 4. Themeans for electrically connecting the LED devices 102, including theends of the wiring, is disposed in the second region 420 s of themulti-functional module 420 g 4. In yet another embodiment, thehypothetical set of parallel planes intersect the enclosure 108 at thespace between adjacent LED devices 102. The LED device 102 is disposedexclusively in the first region 420 f of the multi-functional module 420g 4. A portion of the means for electrically connecting the LED devices102, including the ends of the wiring, is disposed in the first region420 f of the multi-functional module 420 g 4; the other portion of themeans for electrically connecting the LED devices 102, excluding theends of the wiring, is disposed in the second region 420 s of themulti-functional module 420 g 4. Depending on applications, the firstregion 420 f of the multi-functional module 420 g 4 is configured tohave a different set of properties from that of the second region 420 sof the multi-functional module 420 g 4. In an embodiment, the firstregion 420 f of the multi-functional module 420 g 4 is made harder thanthe second region 420 s of the multi-functional module 420 g 4 by, forexample, embedding a greater concentration of phosphor particles in thefirst region 420 f of the multi-functional module 420 g 4 than in thesecond region 420 s of the multi-functional module 420 g 4. The firstregion 420 f of the multi-functional module 420 g 4, because it isharder, is thus configured to better protect the linear array of LEDdevices 102 from malfunctioning when the LED filament 100 is bent tomaintain a desired posture in a light bulb. The second region 420 s ofthe multi-functional module 420 g 4 is made softer for keeping theentire LED filament 100 as bendable in the light bulb as it requires forgenerating omnidirectional light with, preferably, exactly one LEDfilament 100. In another embodiment, the first region 420 f of themulti-functional module 420 g 4 has greater thermal conductivity thanthe second region 420 s of the multi-functional module 420 g 4 by, forexample, doping a greater concentration of nanoparticles in the firstregion 420 f of the multi-functional module 420 g 4 than in the secondregion 420 s of the multi-functional module 420 g 4. The first region420 f of the multi-functional module 420 g 4, having greater thermalconductivity, is thus configured to better protect the linear array ofLED devices 102 from degrading or burning by removing excess heat fromthe LED device 102. The second region 420 s of the multi-functionalmodule 420 g 4, because it is spaced apart from the linear array of LEDdevices 102, plays a lesser role than the first region 420 f of themulti-functional module 420 g 4 in cooling the LED device 102. The costfor making the LED filament 100 is thus economized when the secondregion 420 s of the multi-functional module 420 g 4 is not as heavilydoped with nanoparticles as the first region 420 f of themulti-functional module 420 g 4. The dimension of the first region 420 fof the multi-functional module 420 g 4, in which the LED device 102 isdisposed, in relation to the entire enclosure 108 is determined by adesired totality of considerations such as light conversion capability,bendability and thermal conductivity. Other things equal, the bigger thefirst region 420 f of the multi-functional module 420 g 4 in relation tothe entire enclosure 108, the LED filament 100 has greater lightconversion capability and thermal conductivity but will be lessbendable. An outer surface of the enclosure 108 shows a combination ofthe first region 420 f of the multi-functional module 420 g 4 and otherregions of the multi-functional module 420 g 4. R15 is a ratio of thetotal area of the first regions 420 f of the multi-functional modules420 g 4 found on the outer surface to the overall area of the outersurface of the enclosure 108. Preferably, R15 is from 0.2 to 0.8. Mostpreferably, R15 is from 0.4 to 0.6.

The ways illustrated above in which an enclosure is divided intomodules, including a multi-functional module, having distinctiveproperties can be employed in combination with one another, in FIGS. 27and 29 as examples, to functionalize an LED filament 100 as desired. InFIG. 27, the truncated LED filament 100 is further carved into a smallportion and a big portion to show its internal structure. The smallportion is defined by revolving the rectangle ABCD around the line CD(i.e. the longitudinal axis of the LED filament 100) for 90 degrees.Likewise, the big portion is defined by revolving the rectangle ABCDaround the line CD for the entirety of 360 degrees except for the spacetaken by the small portion. For example, the enclosure 108 ismodularized with a first set of hypothetical planes. The module thusdefined is further regionalized with a second set of hypothetical planesand with a third set of hypothetical planes. The first set ofhypothetical planes intersect the enclosure 108 perpendicularly to thelongitudinal axis of the enclosure 108. For example, the enclosure 108includes two alternating multi-functional modules 420 f, 420 s, i.e. afirst multi-functional module 420 f and a second multi-functional module420 s, defined by the hypothetical set of parallel planes. In anembodiment, the hypothetical set of parallel planes intersect theenclosure 108 right at the edges of an LED device 102. The LED device102 is disposed exclusively in the first multi-functional module 420 f.The means for electrically connecting the LED devices 102, e.g. the bondwire, is disposed exclusively in the second multi-functional module 420s. In another embodiment, the hypothetical set of parallel planesintersect the enclosure 108 between the edges of an LED device 102. Aportion of the LED device 102, excluding the edges, is disposed in thefirst multi-functional module 420 f; the other portion of the LED device102, including the edges, is disposed in the second multi-functionalmodule 420 s. The means for electrically connecting the LED devices 102,including the ends of the wiring, is disposed in the secondmulti-functional module 420 s. In yet another embodiment, thehypothetical set of parallel planes intersect the enclosure 108 at thespace between adjacent LED devices 102. The LED device 102 is disposedexclusively in the first multi-functional module 420 f. A portion of themeans for electrically connecting the LED devices 102, excluding theends of the wiring, is disposed in the second multi-functional module420 s; the other portion of the means for electrically connecting theLED devices 102, including the ends of the wiring, is disposed in thefirst multi-functional module 420 f. Depending on applications, thefirst multi-functional module 420 f is configured to have a differentset of properties from that of the second multi-functional module 420 s.In an embodiment, the first multi-functional module 420 f is made harderthan the second multi-functional module 420 s by, for example, embeddinga greater concentration of phosphor particles in the firstmulti-functional module 420 f than in the second multi-functional module420 s. The first multi-functional module 420 f, because it is harder, isthus configured to better protect the linear array of LED devices 102from malfunctioning when the LED filament 100 is bent to maintain adesired posture in a light bulb. The second multi-functional module 420s is made softer for keeping the entire LED filament 100 as bendable inthe light bulb as it requires for generating omnidirectional light with,preferably, exactly one LED filament 100. In another embodiment, thefirst multi-functional module 420 f has greater thermal conductivitythan the second multi-functional module 420 s by, for example, doping agreater concentration of nanoparticles in the first multi-functionalmodule 420 f than in the second multi-functional module 420 s. The firstmulti-functional module 420 f, having greater thermal conductivity, isthus configured to better protect the linear array of LED devices 102from degrading or burning by removing excess heat from the LED device102. The second multi-functional module 420 s, because it is spacedapart from the linear array of LED devices 102, plays a lesser role thanthe first multi-functional module 420 f in cooling the LED device 102.The cost for making the LED filament 100 is thus economized when thesecond multi-functional module 420 s is not as heavily doped withnanoparticles as the first multi-functional module 420 f. The dimensionof the first multi-functional module 420 f, in which the LED device 102is disposed, in relation to the entire enclosure 108 is determined by adesired totality of considerations such as light conversion capability,bendability and thermal conductivity. Other things equal, the bigger thefirst multi-functional module 420 f in relation to the entire enclosure108, the LED filament 100 has greater light conversion capability andthermal conductivity but will be less bendable.

Staying on FIG. 27, the second set of hypothetical planes intersect theenclosure 108 perpendicularly to the light illuminating direction of thelinear array of LED devices 102. For example, the multi-functionalmodule 420 f, 420 s descried above includes three regions 420 u, 420 hm,420 w defined by a hypothetical pair of planes compartmentalizing themulti-functional module 420 f, 420 s into an upper region 420 u, a lowerregion 420 w and a horizontal middle region 420 hm sandwiched by theupper region 420 u and the lower region 420 w. The linear array of LEDdevices 102 is disposed exclusively in one of the regions of themulti-functional module. Alternatively, the linear array of LED devices102 is absent from at least one of the regions of the multi-functionalmodule. Alternatively, the linear array of LED devices 102 is disposedin all regions of the multi-functional module. Staying on FIG. 27, thelinear array of LED devices 102 is disposed exclusively in thehorizontal middle region 420 hm of the multi-functional module 420 f,420 s and is spaced apart by the horizontal middle region 420 hm fromthe top region 420 u and the lower region 420 w. In an embodiment, thehorizontal middle region 420 hm includes a wavelength converter forconverting blue light emitting from the LED device 102 into white light.The upper region 420 u includes a cylindrical lens for aligning thelight beaming upwards. The lower region 420 w includes a cylindricallens for aligning the light beaming downwards. In another embodiment,the horizontal middle region 420 hm is made harder than the upper region420 u, the lower region 420 w or both by, for example, embedding agreater concentration of phosphor particles in the horizontal middleregion 420 hm than in the upper region 420 u, the lower region 420 w orboth. The horizontal middle region 420 hm, because it is harder, is thusconfigured to better protect the linear array of LED devices 102 frommalfunctioning when the LED filament 100 is bent to maintain a desiredposture in a light bulb. The upper region 420 u (or the lower region 420w) is made softer for keeping the entire LED filament 100 as bendable inthe light bulb as it requires for generating omnidirectional light withpreferably exactly one LED filament 100. In yet another embodiment, thehorizontal middle region 420 hm has greater thermal conductivity thanthe upper region 420 u, the lower region 420 w or both by, for example,doping a greater concentration of nanoparticles in the horizontal middleregion 420 hm than in the upper region 420 u, the lower region 420 w orboth. The horizontal middle region 420 hm, having greater thermalconductivity, is thus configured to better protect the linear array ofLED devices 102 from degrading or burning by removing excess heat fromthe LED device 102. The upper region 420 u (or the lower region 420 w),because it is spaced apart from the linear array of LED devices 102,plays a lesser role than the horizontal middle region 420 hm in coolingthe LED device 102. The cost for making the LED filament 100 is thuseconomized when the upper region 420 u (or the lower region 420 w) isnot as heavily doped with nanoparticles as the horizontal middle region420 hm. The dimension of the horizontal middle region 420 hm, in whichthe linear array of LED devices 102 is exclusively disposed, in relationto the entire enclosure 108 is determined by a desired totality ofconsiderations such as light conversion capability, bendability andthermal conductivity. Other things equal, the bigger the horizontalmiddle region 420 hm in relation to the entire enclosure 108, the LEDfilament 100 has greater light conversion capability and thermalconductivity but will be less bendable.

Staying on FIG. 27, the third set of hypothetical planes intersect theenclosure 108 parallelly to the light illuminating direction of thelinear array of LED devices 102. For example, the multi-functionalmodule 420 f, 420 s described above includes three regions 420 l, 420vm, 420 r defined by a hypothetical pair of planes compartmentalizingthe multi-functional module 420 f, 420 s into a right region 420 r, aleft region 420 l and a vertical middle region 420 vm sandwiched by theright region 420 r and the left region 420 l. The linear array of LEDdevices 102 is disposed exclusively in one of the regions of themulti-functional module 420 f, 420 s. Alternatively, the linear array ofLED devices 102 is absent from at least one of the regions of themulti-functional module 420 f, 420 s. Alternatively, the linear array ofLED devices 102 is disposed in all regions of the multi-functionalmodule 420 f, 420 s. In FIG. 27, the linear array of LED devices 102 isdisposed exclusively in the vertical middle region 420 vm of themulti-functional module 420 f, 420 s and is spaced apart by the verticalmiddle region 420 vm from the right region 420 r and the left region 420l. In an embodiment, the vertical middle region 420 vm includes awavelength converter for converting blue light emitting from the LEDdevice 102 into white light. The right region 420 r includes acylindrical lens for aligning the light beaming rightwards. The leftregion 420 l includes a cylindrical lens for aligning the light beamingleftwards. In another embodiment, the vertical middle region 420 vm ismade harder than the right region 420 r, the left region 420 l or bothby, for example, embedding a greater concentration of phosphor particlesin the vertical middle region 420 vm than in the right region 420 r, theleft region 420 l or both. The vertical middle region 420 vm, because itis harder, is thus configured to better protect the linear array of LEDdevices 102 from malfunctioning when the LED filament 100 is bent tomaintain a desired posture in a light bulb. The right region (or theleft region) is made softer for keeping the entire LED filament 100 asbendable in the light bulb as it requires for generating omnidirectionallight with, preferably, exactly one LED filament 100. In yet anotherembodiment, the vertical middle region 420 vm has greater thermalconductivity than the right region 420 r, the left region 420 l or bothby, for example, doping a greater concentration of nanoparticles in thevertical middle region 420 vm than in the right region 420 r, the leftregion 420 l or both. The vertical middle region 420 vm, having greaterthermal conductivity, is thus configured to better protect the lineararray of LED devices 102 from degrading or burning by removing excessheat from the LED device 102. The right region 420 r (or the left region420 l), because it is spaced apart from the linear array of LED devices102, plays a lesser role than the vertical middle region 420 vm incooling the LED device 102. The cost for making the LED filament 100 isthus economized when the right region 420 r (or the left region 420 l)is not as heavily doped with nanoparticles as the vertical middle region420 vm. The dimension of the vertical middle region 420 vm, in which thelinear array of LED devices 102 is exclusively disposed, in relation tothe entire enclosure 108 is determined by a desired totality ofconsiderations such as light conversion capability, bendability andthermal conductivity. Other things equal, the bigger the vertical middleregion 420 vm in relation to the entire enclosure 108, the LED filament100 has greater light conversion capability and thermal conductivity butwill be less bendable.

Shifting to FIG. 28, the truncated LED filament 100 is further carvedinto a small portion and a big portion to show its internal structure.The small portion is defined by revolving the rectangle ABCD around theline CD (i.e. the longitudinal axis of the LED filament 100) for afraction of 360 degrees. Likewise, the big portion is defined byrevolving the rectangle ABCD around the line CD for the entirety of 360degrees except for the space taken by the small portion. In anembodiment, the enclosure 108 is modularized and regionalized with, forexample, a hypothetical set of cylindrical surfaces in combination witha hypothetical set of planes. First, the multifunctional modules of theenclosure 108 are defined by a hypothetical set of parallel planesintersecting the enclosure 108 perpendicularly to the longitudinal axisof the enclosure 108. For example, the enclosure 108 includes twoalternating multifunctional modules 420 f, 420 s, i.e. a first module420 f and a second module 420 s, defined by the hypothetical set ofparallel planes. In an embodiment, the hypothetical set of parallelplanes intersect the enclosure 108 right at the edges of the LED device102. The LED device 102 is disposed exclusively in the first module 420f. The means for electrically connecting the LED devices 102, e.g. thebond wire, is disposed exclusively in the second module 420 s. Inanother embodiment, the hypothetical set of parallel planes intersectthe enclosure 108 between the edges of the LED device 102. A portion ofthe LED device 102, excluding the edges, is disposed in the first module420 f; the other portion of the LED device 102, including the edges, isdisposed in the second module 420 s. The means for electricallyconnecting the LED devices 102, including the ends of the wiring, isdisposed in the second module 420 s. In yet another embodiment, thehypothetical set of parallel planes intersect the enclosure 108 at thespace between adjacent LED devices 102. The LED device 102 is disposedexclusively in the first module 420 f. A portion of the means forelectrically connecting the LED devices 102, excluding the ends of thewiring, is disposed in the second module 420 s; the other portion of themeans for electrically connecting the LED devices 102, including theends of the wiring, is disposed in the first module 420 f. Depending onapplications, the first module 420 f is configured to have a differentset of properties from that of the second module 420 s. In anembodiment, the first module 420 f is made harder than the second module420 s by, for example, embedding a greater concentration of phosphorparticles in the first module 420 f than in the second module 420 s. Thefirst module 420 f, because it is harder, is thus configured to betterprotect the linear array of LED devices 102 from malfunctioning when theLED filament 100 is bent to maintain a desired posture in a light bulb.The second module 420 s is made softer for keeping the entire LEDfilament 100 as bendable in the light bulb as it requires for generatingomnidirectional light with, preferably, exactly one LED filament 100. Inanother embodiment, the first module 420 f has greater thermalconductivity than the second module 420 s by, for example, doping agreater concentration of nanoparticles in the first module 420 f than inthe second module 420 s. The first module 420 f, having greater thermalconductivity, is thus configured to better protect the linear array ofLED devices 102 from degrading or burning by removing excess heat fromthe LED device 102. The second module 420 s, because it is spaced apartfrom the linear array of LED devices 102, plays a lesser role than thefirst module 420 f in cooling the LED device 102. The cost for makingthe LED filament 100 is thus economized when the second module 420 s isnot as heavily doped with nanoparticles as the first module 420 f. Thedimension of the first module 420 f, in which the LED device 102 isdisposed, in relation to the entire enclosure 108 is determined by adesired totality of considerations such as light conversion capability,bendability and thermal conductivity. Other things equal, the bigger thefirst module 420 f in relation to the entire enclosure 108, the LEDfilament 100 has greater light conversion capability and thermalconductivity but will be less bendable.

Next, the regions of the multifunctional module are defined by ahypothetical set of coaxial cylindrical surfaces having the longitudinalaxis of the LED filament 100 as their central axis. For example, theenclosure 108 includes three regions 420 e, 420 m, 420 o defined by ahypothetical pair of coaxial cylindrical surfaces compartmentalizing themultifunctional module 420 f, 420 s into a core region 420 e, an outerregion 420 o and a tubular middle region 420 m sandwiched by the coreregion 420 e and the outer module 420 o. The linear array of LED devices102 is disposed exclusively in one of the regions of the multifunctionalmodule. Alternatively, the linear array of LED devices 102 is absentfrom at least one of the regions of the multifunctional module.Alternatively, the linear array of LED devices 102 is disposed in allregions of the multifunctional module. In an embodiment, the outerregion 420 o includes a light scatterer for increasing light extractionfrom the LED device 102 by reducing total internal reflection. Thetubular middle region 420 m includes a wavelength converter forconverting blue light emitting from the LED device 102 into white light.The core region 420 e includes a spacer. The spacer prevents heat comingfrom the LED device 102 from quickly degrading the phosphor particle bykeeping the phosphor particle apart from the LED device 102. Moreover,the spacer enables a uniform thickness for the tubular middle region 420m, which includes the wavelength converter, to produce uniform whitelight, which entails a proper combination of blue light and the phosphorlight. In another embodiment, the tubular middle region 420 m is madeharder than the core region 420 e, the outer region 420 o or both by,for example, embedding a greater concentration of phosphor particles inthe tubular middle region 420 m than in the core region 420 e, the outerregion 420 o or both. The tubular middle region 420 m, because it isharder, is thus configured to better protect the linear array of LEDdevices 102 from malfunctioning when the LED filament 100 is bent tomaintain a desired posture in a light bulb. The core region 420 e (orthe outer region 420 o) is made softer for keeping the entire LEDfilament 100 as bendable in the light bulb as it requires for generatingomnidirectional light with, preferably, exactly one LED filament 100. Inyet another embodiment, the core region 420 e has greater thermalconductivity than the tubular middle region 420 m, the outer region 420o or both by, for example, doping a greater concentration ofnanoparticles in the core region 420 e than in the tubular middle region420 m, the outer region 420 o or both. The core region 420 e, havinggreater thermal conductivity, is thus configured to better protect thelinear array of LED devices 102 from degrading or burning by removingexcess heat from the LED device 102. The tubular middle region 420 m (orthe outer region 420 o), because it is spaced apart from the lineararray of LED devices 102, plays a lesser role than the core region 420 ein cooling the LED device 102. The cost for making the LED filament 100is thus economized when the tubular middle region 420 m (or the outerregion 420 o) is not as heavily doped with nanoparticles as the coreregion 420 e. The dimension of the core region 420 e, in which thelinear array of LED devices 102 is exclusively disposed, in relation tothe entire enclosure 108 is determined by a desired totality ofconsiderations such as light conversion capability, bendability andthermal conductivity. Other things equal, the bigger the core region 420e in relation to the entire enclosure 108, the LED filament 100 has lesslight conversion capability and thermal conductivity but will be morebendable. The dimension of the tubular middle region 420 m, whichincludes the wavelength converter, in relation to the entire enclosure108 is determined by a desired totality of considerations such as lightconversion capability, bendability and thermal conductivity. Otherthings equal, the bigger the tubular middle region 420 m in relation tothe entire enclosure 108, the LED filament 100 has greater lightconversion capability and thermal conductivity but will be lessbendable.

The region of a multifunctional module defined by the hypothetical setof cylindrical surfaces and the hypothetical set of planes is eithercontinuous or not continuous. Shifting to FIG. 29, in an embodiment, thecore region 420 e and the tubular middle region 420 m extendlongitudinally across the first module 420 f of the enclosure 108 butare broken periodically and absent from the second module 420 s. Inother words, what would be a tubular middle region and a core region ifthe all regions were continuous throughout second module 420 s aremerged into one region in the second module 420 s when all regions ofthe multifunctional modules 420 f, 420 s are not continuous. Staying onFIG. 29, what would otherwise be a core module 420 e and a tubularmiddle module 420 m in the first module 420 f in FIG. 28 become a coreregion 420 e and a tubular middle region 420 m in the multifunctionalmodule 420 f. For example, the outer module 420 o, which is continuousthroughout the enclosure 108, includes a light scatterer for reducingtotal internal reflection. The multi-functional module 420 f includes atubular middle region 420 m and a core region 420 e. The tubular middleregion 420 m of the multi-functional module 420 f—sandwiched by theouter module 420 o and the core region 420 e of the multifunctionalmodule 420 f—includes a wavelength converter, e.g. phosphor particlesembedded in a transparent binder, for producing uniform white light,which entails a proper combination of blue light and the phosphor light.The core region 420 e of the multifunctional module 420 f includes aspacer for preventing heat coming from the LED device 102 from degradingthe phosphor particles in the wavelength converter prematurely.Moreover, the spacer enables a uniform thickness for the tubular middleregion 420 m of the multifunctional module 420 f. The second module 420s, like the core region 420 e of the multifunctional module 420 f, alsoincludes a wavelength converter. In an embodiment, the second module 420s is softer than the core region 420 e of the multifunctional module 420f, the tubular middle region 420 m of the multifunctional module 420 for both such that the LED filament 100 is as bendable as it is requiredto generate omnidirectional light with exactly one LED filament 100. Inanother embodiment, the second module 420 s is less thermally conductivethan the core region 420 e of the multifunctional module 420 f, thetubular middle region 420 m of the multifunctional module 420 f or both.The core region 420 e of the multifunctional module 420 f (or thetubular middle region 420 m of the multifunctional module 420 f) plays abigger role than the second module 420 s in removing heat generated bythe LED device 102. Related features are described in FIGS. 49A to 54and 56 in U.S. Pat. No. 15/499,143 filed Apr. 27, 2017.

FIG. 33 shows an LED light bulb 20 having an LED filament 100 of thepresent invention as the light source. In an embodiment, the LED lightbulb 20 comprises a light transmissive envelope (i.e. bulb shell, bulbhousing) 12, a base 16, a stem press 19, an LED filament 100 and aplurality of lead wires 51. The light transmissive envelope 12 is abulbous shell made from light transmissive materials such as glass andplastic. The light transmissive envelope 12 includes a bulbous mainchamber 1250 for housing the LED filament 100 and sometimes a neck 12 ndimensionally adapted for attaching to the base 16. At least part of thebase 16 is metal and includes a plurality of electrical contacts 526 forreceiving electrical power from a lampholder. In FIG. 33, the lighttransmissive envelope 12 is mounted with its neck 12 n on the base 16.The stem press 19 is mounted on the base 16 within the lighttransmissive envelope 12 for holding the lead wire 51 and the LEDfilament 100 in position while keeping the positive and negativecurrents insulated from each other. The lead wire 51 extends in asubstantially axial direction from the base 16 through the neck 12 n allthe way into the main chamber 1250. The lead wires 51 are coupled to theelectrical contacts 526 of the base 16 and an electrical connector 506of the LED filament 100. Electrical power is communicated from thelampholder to the base 16 and all the way to the LED filament 100through the lead wire 51 when the base 16 and the lampholder areproperly connected. The LED light bulb 20 is thus configured to emitlight omnidirectionally. In some embodiments, the LED light bulb 20,including exactly one LED filament 100, is configured to emit lightomnidirectionally. In other embodiments, the LED light bulb 20,including a plurality of LED filaments 100, is configured to emit lightomnidirectionally. In addition to brining electrical power for the LEDfilament 100, the lead wire 51 also supports the LED filament 100 tomaintain a desired posture in the main chamber 1250.

In some embodiment where the lead wire 51 alone cannot providesufficient support, the LED light bulb 20 further includes a pluralityof support wires 15 to help the LED filament 100 maintain a desiredposture in the main chamber 1250. In some embodiments, the support wire15 is made of carbon spring steel for additional damping protection.Preferably, the support wire 15 is not in electrical communication withany part of the LED light bulb 20. Thus, negative impact resulting fromthermal expansion or heat is mitigated. When the LED filament 100defines a sinuous curve in the main chamber 1250, the lead wire 51supports the LED filament 100 either at the crest of the curve, thetrough of the curve or anywhere between the crest and the trough. Thesupport wire 334 attaches to the LED filament 100 in a variety of ways.For example, the lead wire 51 includes a hook or claw at a tip. Thethroat of the hook is snugly closed around the LED filament 100.Alternatively, the claw is snugly closed around the LED filament 100.

Staying on FIG. 33, in an embodiment, the LED light bulb include exactlytwo lead wires 51. The base 16 includes a top end, a bottom end and aside surface. The light transmissive envelope 12 is mounted with itsneck 12 n on the top end of the base 16. The base 16 includes twoelectrical contracts 526 at the bottom end and the side surface. Leadwires 51 are coupled to the electrical contacts of the base 16 and theelectrical connector 506 of the LED filament 100. For example, the leadwire 51 and the electrical connector 506 may be fastened together bysoldering. The filler metal for soldering includes gold, silver,silver-based alloy or tin. Alternatively, when the electrical connector506 includes an aperture and the lead wire 51 includes a hook structureat a tip, the lead wire 51 and the electrical connector 506 is fastenedby closing the throat of the hook against the aperture. In someembodiments, the LED light bulb 20 further includes a driving circuit518 (e.g. rectifier), which is in electrical connection with theelectrical contacts 526 of the base 16 and the lead wire 51, forconverting AC electricity from the lampholder into DC electricity todrive the LED filament 100.

Staying on FIG. 33, preferably, the base 16 has a form factor compatiblewith industry standard light bulb lampholder. Specifications for lightbulb bases and sockets are largely overseen by two organizations. TheAmerican National Standards Institute (ANSI) is an organization thatpublishes C81.61 and C81.62, while International ElectrotechnicalCommission (IEC) publishes 60061-1 and 60061-2. Edison screw lamp baseand lampholder examples include but are not limited to the E-seriesdescribed in ANSI C81.61 and C81.62: E5 midget, E10 miniature, E11mini-candelabra, E12 candelabra, E17 intermediate, E26/24 single-contactmedium, E26d double-contact medium, E26/50x39 skirted medium, E26/53x39extended skirted medium, E29/53x39 extended skirted admedium, E39single-contact mogul, E39d double-contact mogul, EP39 position-orientedmogul, and EX39 exclusionary mogul. Multiple-pin lamp base andlampholder examples include but are not limited to the G-seriesdescribed in ANSI C81.61 and C81.62: GY two-pin for T, G4 two-pin forsingle-ended TH, GU4 two-pin for MR11 GLS lamps, GZ4 two-pin forprojection lamps, G5 fluorescent miniature two-pin, 2G7 four-pin compactfluorescent, GZ10 bipin, G16t three-contact lug for PAR lamps, G17tthree-pin prefocus for incandescent projection lamps. Bayonet lamp baseand lampholder examples include but are not limited to the B-seriesdescribed in ANSI C81.61 and C81.62: B/BX8.4d small instrument panel,BA9/12.5 miniature, BAW9s for HY21W, BA15s candelabra single contact,BAZ15d double contact with offset, and BY22d multipurpose sleeved doublecontact.

Staying on FIG. 33, in an embodiment, the light transmissive envelope 12is made from a light transmissive material with good thermalconductively, e.g. glass, plastic. In another embodiment, the lighttransmissive envelope 12 is configured to absorb a portion of the bluelight emitted by the LED filament 100 to obtain a warmer colortemperature. To make the light warmer, for example, the lighttransmissive envelope 12 is made from a material doped with yellowparticles. Alternatively, the light transmissive envelope 12 is coatedwith a yellow film. In yet another embodiment, the light transmissiveenvelope 12, which is hermetically connected to the base 16, is chargedwith a gas having greater thermal conductivity than the air such ashydrogen, nitrogen and a mixture of both. In additional to greater heatdissipation, humidity—potentially undermining the electronics of the LEDlight bulb 20—is thus removed from the light transmissive envelope 12.In an embodiment, hydrogen accounts for from 5% to 50% of the volume ofthe light transmissive envelope 12. In still another embodiment, thelight transmissive envelope 12 is sealed at an internal pressure of from0.4 to 1.0 ATM.

Staying on FIG. 33, the stem press 19 is made from an electricallyinsulative material such as glass or plastic. The shape and dimension ofthe stem press 19 depends on a totality of considerations such as thenumber of LED filaments 100 the LED light bulb 20 has, the posture theLED filament 100 is expected to maintain in the main chamber 1250; themanner the lead wire 51 supports the LED filament 100; the number oflead wires 51 the LED light bulb 20 has; whether the LED light bulb 20further includes support wires 15; and whether or how a heatsink findsitself in the LED light bulb 20. In an embodiment, the step press 19includes a basal portion 19 b for attaching the stem press 19 to thebase 19 b and a post portion 19 a for attaching the support wire 51 tothe step press 19. The length of the step press 19 depends on theposition the LED filament 100 is expected to be elevated in the lighttransmissive envelope 12. In an embodiment, the stem press 19 extendsbarely above the base 16. In another embodiment, the stem press 19extends above the base 16 and into the neck 12 n. In yet anotherembodiment, the stem press 19 extends above the base 16, through theneck 12 n and into the main chamber 1250. In some embodiments, the stempress 19 is made from an electrically insulative material having goodthermal conductivity such as aluminium oxide and aluminium nitride. Inother embodiments, the stem press 19 includes an opening for evacuatingair from the light transmissive envelope 12 and for charging the lighttransmissive envelope 12 with the desired amount of gas.

Staying on FIG. 33, in some embodiments, the base 16 includes a heatsink17. The heatsink 17 is made from materials having good thermalconductivity such as metal, thermal ceramics and thermal plastic. Insome embodiments, the stem press 19, the portion of the base 16 otherthan the heatsink 17 or both is made from a same material from which theheatsink 17 is made. In other embodiments, an integral piece including acombination of at least two of the stem press 19, the other portion ofthe base 16 other than the heatsink 17 and the heatsink 17 is formedwith a same material to reduce thermal resistance of the LED light bulb20. The heatsink 17 is in thermal communication with the LED filament100 and ambient air for transferring heat coming from the LED device tothe ambient air. Preferably, the heatsink 17 is in thermal communicationwith, in addition to the LED filament 100 and ambient air, the stempress 19, the lead wire 51, the support wire 15, the other portion ofthe base 16 other than the heatsink 17 or any combination of the above.

The LED filament 100 is designed to maintain a posture within thechamber to obtain an omnidirectional light emission. Shifting to FIG.34, the LED light bulb 20 comprises a light transmissive envelope 12, abase 16, a stem press 19, exactly one LED filament 100, exactly a pairof lead wires 51 and a rectifier 518. The rectifier 518 is disposedwithin the space inside the base 16. The stem press 19 includes astump-like structure projecting from the base 16. The LED filament 100defines an arc extending substantially vertically in the lighttransmissive envelope 12. Optionally, the base 16 includes a heatsink17. For easy reference, a Cartesian coordinate system is oriented forthe LED light bulb 20 where: (1) the interface connecting the lighttransmissive envelope 19 a and base 19 b falls on the x-y plane; and (2)the z-axis, also the longitudinal axis of the LED light bulb 20,intersects the interface at point O. In an embodiment, the endpoint ofthe arc reaches as high as point H1 on the z-axis. The distance on they-axis between the endpoints of the LED filament 100 is D. The length ofLED filament 100 on the z-axis is Al. The posture of the LED filament100 in the LED light bulb 20 is defined by all points in the set (0, Y,Z+H1), where Z goes up from 0 to A1 and then from A1 back to 0 as Y goesfrom −D/2 to 0 and then from 0 to D/2. The length of the heatsink 17along the z-axis is L1. The length of the combination of the lighttransmissive envelope 12 and the heatsink 17 along the z-axis is L2. Qis the ratio of L1 to L2. Other things equal, the greater Q is, the LEDlight bulb 20 has stronger heatsinking capability but less space for theLED filament 100 to maintain a suitable posture in the lighttransmissive envelope 12 and shine omnidirectionally. Preferably, Q isfrom 0.1 to 1.5. Most preferably, Q is from 0.2 to 0.4. The curvaceouslength of the LED filament 100 is L. The sinuosity (S) of the LEDfilament 100 is L/D. Other things equal, the greater S is, the closer toan omnidirectional luminary the LED light bulb 20 will be. Preferably, Sis from 1.5 to 4. Most preferably, S is from 2 to 3. M is the ratio ofthe length of the LED filament 100 on the x-axis to the length of thelight transmissive envelope 12 on the x-axis. N is the ratio of thelength of the LED filament 100 on the y-axis to the length of the lighttransmissive envelope 12 on the y-axis. P is the ratio of the length ofthe LED filament 100 on the z-axis to the length of the lighttransmissive envelope 12 on the z-axis. Other things equal, the closerto 3 the aggregate of M, N and P is, the closer to an omnidirectionalluminary the LED light bulb is. In the embodiment, M is from 0 to 0.05.Preferably, N is from 0.1 to 0.8 and P is from 0.1 to 0.8. Mostpreferably, N is from 0.3 to 0.6 and P is from 0.2 to 0.5.

Shifting to FIG. 35, the LED light bulb 20 comprises a lighttransmissive envelope 12, a base 16 including a heatsink 17, a stempress 19, exactly one LED filament 100, exactly a pair of lead wires 51,a rectifier 518 and a plurality of support wires 15. The rectifier 518is disposed within the base 16. The stem press 19 includes a stump-likebasal portion 19 b for attaching the stem press 19 to the base 332 andan elongated post portion 19 a for elevating the LED filament 100 to adesired position in the light transmissive envelope 12. The plurality ofsupport wires 15 radiates (horizontally, for example) from the postportion 19 a to form a spoke-and-hub structure in the light transmissiveenvelope 12. The support wire 15 is attached to the post portion 19 a ata first end and to the LED filament 100 at a second end. In theembodiment, the LED filament 100 defines a sinuous curve along an arcmeandering in the light transmissive envelope 12. The sinuous curvedefined by the LED filament 100 oscillates in the range from H2+A2 toH2−A2 on the z-axis, where H2 represents the average height of the LEDfilament 100 along the z-axis in the LED light bulb 20 and A2 theamplitude of the sinuous curve the LED filament 100 defines. Theplurality of support wires 15 has a same length R. The posture of theLED filament 100 in the LED light bulb 20 is defined by all points inthe set (X, Y, Z+H2), where −R=<X=<R; −R=<Y=<R; and −A2=<Z=<A2. The LEDfilament 100, seen through the light transmissive envelope 12, isaesthetically pleasing whether it is glowing or not. Moreover,omnidirectional light emission is made possible with only one LEDfilament 100 having a posture like this. The quality as well the costfor producing omnidirectional LED light bulbs 20 is thus improvedbecause fewer interconnections of parts are needed when only one LEDfilament 100 is employed. The length between the endpoints of the LEDfilament 100 is D. The actual length of the LED filament 100 is L. Thesinuosity (S) of the LED filament 100 is L/D. Other things equal, thegreater S is, the closer to an omnidirectional luminary the LED lightbulb 20 will be. Preferably, S is from 2 to 20. Most preferably, S isfrom 4 to 6. M is the ratio of the length of the LED filament 100 on thex-axis to the length of the light transmissive envelope 12 on thex-axis. N is the ratio of the length of the LED filament 100 on they-axis to the length of the light transmissive envelope 12 on they-axis. P is the ratio of the length of the LED filament 100 on thez-axis to the length of the light transmissive envelope 12 on thez-axis. In the embodiment, P is from 0.2 to 0.7. Preferably, P is from0.3 to 0.6. Preferably, M is from 0.2 to 0.8 and N is from 0.2 to 0.8.Most preferably, M is from 0.3 to 0.4 and N is from 0.3 to 0.4.

Shifting to FIG. 36, the LED light bulb 20 comprises a lighttransmissive envelope 12, a base 16, a stem press 19, exactly one LEDfilament 100, exactly a pair of lead wires 51, a rectifier 518 and aplurality of support wires 15. The light transmissive envelope 12 has abulbous main chamber 1250 for housing the LED filament 100 and a neck 12n for connecting the light transmissive envelope 12 to the base 16. Therectifier 518 is disposed within the base 16. The plurality of supportwires 15 radiates (slightly deviating from the horizon, for example)from the post portion 19 a of the stem press 19 to form a spoke-and-hubstructure inside the light transmissive envelope 12. The support wire 15is attached to the post portion 19 a at a first end and to the LEDfilament 100 at a second end. In the embodiment, the LED filament 100defines a sinuous curve along an arc meandering in the lighttransmissive envelope 12. The sinuous curve oscillates in the range fromH3+A3 to H3−A3 on the z-axis, where H3 represents the average height ofthe LED filament 100 in the LED light bulb and A3 the amplitude of thesinuous curve the LED filament 100 defines. A3 is greater than A2;likewise, H3 is greater than H2. Consequently, the stem press 19 inFIGS. 34 and 35 is a shorter structure projecting from projecting fromthe base 16. By contrast, the stem press 333 we need in FIG. 36 toelevate the LED filament 100 to a higher position in the main chamber1250 becomes a longer structure having a basal portion 19 b and anelongated post portion 19 a. The plurality of support wires 15 has asame length R. The posture of the LED filament 100 in the LED light bulb20 is defined by all points in the set (X, Y, Z+H3), where −R=<X=<R;−R=<Y=<R; and −A3=<Z=<A3. The length between the endpoints of the LEDfilament 100 is D. The length of the actual length of the LED filament100 is L. The sinuosity (S) of the LED filament 100 is L/D. Other thingsequal, the greater S is, the closer to an omnidirectional luminary theLED light bulb 20 will be. Preferably, S is from 2 to 20. Mostpreferably, S is from 10 to 14. M is the ratio of the length of the LEDfilament 100 on the x-axis to the length of the light transmissiveenvelope 12 on the x-axis. N is the ratio of the length of the LEDfilament 100 on the y-axis to the length of the light transmissiveenvelope 12 on the y-axis. P is the ratio of the length of the LEDfilament 100 on the z-axis to the length of the light transmissiveenvelope 12 on the z-axis. In the embodiment, P is from 0.2 to 0.7.Preferably, P is from 0.2 to 0.4. Preferably, M is from 0.2 to 0.8 and Nis from 0.2 to 0.8. Most preferably, M is from 0.3 to 0.4 and N is from0.3 to 0.4.

Shifting to FIG. 37, the LED light bulb comprises a light transmissiveenvelope, a base, a stem press, an upper LED filament 100 u, a lower LEDfilament 100 w, a set of lead wires 51, a rectifier 518, an upper set ofsupport wires 100 u and a lower set of support wires 100 w. The lighttransmissive envelope 12 has a bulbous main chamber 1250 for housing theLED filaments 100 u, 100 w and a neck 12 n for connecting the lighttransmissive envelope 12 to the base 16. The rectifier 518 is disposedwithin the base 16. The set of support wires 15 u, 15 w radiate(slightly deviating from the horizon, for example) from the post portion19 a to form a spoke-and-hub structure in the light transmissiveenvelope 12. The support wire 15 u, w is attached to the post portion 19a at a first end and to the LED filament 100 u, 100 w at a second end.The upper set of support wires 15 u is configured to hold the upper LEDfilament 100 u in position. The lower set of support wires 15 w isconfigured to hold the lower LED filament 100 w in position. Otherthings equal, a shorter LED filament 100 is needed to produce the sameluminosity of omnidirectional light with the LED light bulb 20 in FIG.37 than the LED light bulb 20 in FIG. 36. Likewise, the LED light bulb20 in FIG. 37 is amenable to a smaller girth than the LED light bulb 20in FIG. 36. In the embodiment, the LED filament 100 defines a sinuouscurve along an arc meandering in the light transmissive envelope 20. Theupper LED filament 100 u defines an upper sinuous curve oscillating inthe range from H4+A4 to H4−A4 on the z-axis, where H4 represents theaverage height of the upper LED filament 100 u in the LED light bulb 20and A4 the amplitude of the upper sinuous curve the upper LED filament100 u defines. The lower LED filament 100 w defines a lower sinuouscurve oscillating in the range from H5+A5 to H5−A5 on the z-axis, whereH5 represents the average height of the lower LED filament 100 w in theLED light bulb 20 and A5 the amplitude of the lower sinuous curve thelower LED filament 100 w defines. H5 is less than H4, making the upperLED filament 100 u higher in the light transmissive envelope 12 than thelower LED filament 100 w. A4 is chosen to be, for example, the same asA5. The plurality of support wires 15 u, 15 w have a same length R. Theposture of the upper LED filament 100 u in the LED light bulb 20 isdefined by all points in the set (X, Y, Z+H4), where −R=<X=<R; −R=<Y=<R;and −A4=<Z=<A4. The posture of the lower LED filament 100 w in the LEDlight bulb 20 is defined by all points in the set (X, Y, Z+H5), where−R=<X=<R; −R=<Y=<R; and −A5 Z=<A5. The length of between the endpointsof the LED filament 100 u, 100 w is D. The length of the actual lengthof the LED filament 100 u, 100 w is L. The sinuosity (S) of the LEDfilament 100 u, 100 w is L/D. Other things equal, the greater S is, thecloser to an omnidirectional luminary the LED light bulb 20 will be.Preferably, S is from 2 to 20. Most preferably, S is from 12 to 16. M isthe ratio of the aggregate of the lengths of the pair of LED filaments100 u, 100 w on the x-axis to the length of the light transmissiveenvelope 12 on the x-axis. N is the ratio of the aggregate of thelengths of the pair of LED filaments 100 u, 100 w on the y-axis to thelength of the light transmissive envelope 12 on the y-axis. P is theratio of the aggregate of the lengths of the pair of the LED filaments100 u, 100 w on the z-axis to the length of the light transmissiveenvelope 12 on the z-axis. In an embodiment, P is from 0.4 to 1.7.Preferably, M is from 0.4 to 1.6 and N is from 0.4 to 1.6. Mostpreferably, M is from 0.6 to 0.8 and N is from 0.6 to 0.8. Relatedfeatures are described in FIGS. 44A to 46B and 47A to 48D in U.S. Ser.No. 15/499,143 filed Apr. 27, 2017.

What is claimed is:
 1. An LED filament, comprising: an enclosure; alinear array of LED devices; and an electrical connector, wherein: theenclosure includes an optically transmissive binder; and the linear ofLED devices is conformally wrapped around by the enclosure to beoperable to emit light when energized through the electrical connector.2. The LED filament in claim 1, wherein the LED filament is capable ofself-sustained plastic deformation for maintaining a suitable posture inan LED light bulb.
 3. The LED filament in claim 2, wherein the LEDfilament maintains the suitable posture in the LED light bulb byphysically attaching the electrical connector to a lead wire of the LEDlight bulb.
 4. The LED filament in claim 2, wherein the enclosureincludes a posture maintainer.
 5. The LED filament in claim 4, whereinthe posture maintainer includes a pre-determined concentration ofparticles harder than the optically transmissive binder in which theparticles are embedded.
 6. The LED filament in claim 5, wherein theposture maintainer includes a pre-determined concentration of phosphorparticles.
 7. The LED filament in claim 6, wherein the enclosureincludes alternate coatings of the optically transmissive binder and thephosphor particles.
 8. The LED filament in claim 4, wherein the posturemaintainer includes a wire system embedded in the optically transmissivebinder.
 9. The LED filament in claim 4, wherein the posture maintainerincludes an aperture system beneath a surface of the enclosure wheretight turns are planned for the posture the LED filament is designed tomaintain in the LED light bulb.
 10. The LED filament in claim 2,wherein: the enclosure is fabricated and tested independently of thelinear array of LED devices; and the enclosure is adhesively bonded tothe linear array of LED devices to form the LED filament in a unitarystructure.
 11. The LED filament in claim 1, wherein the enclosure has atexturized outer surface for improving light extraction.
 12. The LEDfilament in claim 1, wherein the enclosure has a texturized innersurface for improving light extraction.
 13. The LED filament in claim 1,wherein the LED device has a texturized light emission surface forimproving light extraction.
 14. The LED filament in claim 1, wherein anLED die in the LED device has an elongated top view approximating ahypothetical rectangle having a longitudinal axis substantially parallelto a longitudinal axis of the linear array of LED devices.
 15. The LEDfilament in claim 14, wherein an aspect ratio of the hypotheticalrectangle is from 2:1 to 10:1.
 16. The LED filament in claim 1, wherein:the LED devices are interconnected with a bond wire; and a sinuosity ofthe bond wire is from 2 to
 8. 17. The LED filament in claim 1, wherein:the LED devices are interconnected with a glue wire; and a sinuosity ofthe glue wire is from 3 to
 8. 18. The LED filament in claim 1, wherein:the LED devices are interconnected with a flexible printed circuit filmhaving a plurality of conductive tracks; and a ratio of a total areacovered by the plurality of conductive tracks to an area of the flexibleprinted circuit film is from 0.1% to 20%.
 19. The LED filament in claim1, wherein: the enclosure further includes a wavelength converter; thewavelength converter is formed by embedding a plurality of lightconversion particles in the optically transmissive binder; and theplurality of light conversion particles is in a state of optimalconversion.
 20. The LED filament in claim 1, wherein: the enclosurefurther includes a wavelength converter; the wavelength converter isformed by embedding a plurality of light conversion particles in theoptically transmissive binder; and the plurality of light conversionparticles is in a state of thermal optimum for forming a plurality ofheat transfer paths.
 21. The LED filament in claim 20, wherein theplurality of heat transfer paths radiates like spokes of a wheel fromthe LED device like a hub of the wheel.
 22. The LED filament in claim19, wherein a ratio of a volume of the light conversion particles in thewavelength converter to a volume of the optically transmissivetransparent binder in the wavelength converter is from 20:80 to 99:1.23. The LED filament in claim 19, wherein a ratio of a weight of thelight conversion particles in the wavelength converter to a weight ofthe optically transmissive binder in the wavelength converter is from20% to 50%.
 24. An LED filament, comprising: an enclosure; a lineararray of LED devices; and an electrical connector, wherein the entireenclosure is a monolithic structure made from a single piece ofoptically transmissive material.
 25. The LED filament in claim 24,wherein the enclosure includes a first region and a second region havinga different set of properties from that of the first region.
 26. The LEDfilament in claim 25, wherein the regions of the enclosure are definedby a hypothetical plane perpendicular to a light illuminating directionof the linear array of LED devices.
 27. The LED filament in claim 26,wherein: the enclosure includes three regions defined by a pair of thehypothetical planes compartmentalizing the enclosure into an upperregion, a lower region and a middle region sandwiched by the upperregion and the lower region; the linear array of LED devices is disposedin the middle region; a cross section perpendicular to a longitudinalaxis of the LED filament reveals the middle region and other regions ofthe enclosure; R1 is a ratio of an area of the middle region to anoverall area of the cross section; and R1 is from 0.2 to 0.8.
 28. TheLED filament in claim 25, wherein the regions of the enclosure aredefined by a hypothetical plane parallel to a light illuminatingdirection of the linear array of LED devices.
 29. The LED filament inclaim 28, wherein: the enclosure includes three regions defined by apair of the hypothetical planes compartmentalizing the enclosure into aright region, a left region and a middle region sandwiched by the rightregion and the left region; the linear array of LED devices is disposedin the middle region; a cross section perpendicular to a longitudinalaxis of the LED filament reveals the middle region and other regions ofthe enclosure; R2 is a ratio of an area of the middle region to anoverall area of the cross section; and R2 is from 0.2 to 0.8.
 30. TheLED filament in claims 25, wherein the regions of the enclosure aredefined by a hypothetical cylindrical surface having a central axis ofthe LED filament as its central axis.
 31. The LED filament in claim 30,wherein: the enclosure includes three regions defined by a coaxial pairof the hypothetical cylindrical surfaces compartmentalizing theenclosure into a core region, an outer region and a middle regionsandwiched by the core region and the outer region; and the linear arrayof LED devices is disposed in the core region.
 32. The LED filament inclaim 31, wherein: a cross section perpendicular to a longitudinal axisof the LED filament reveals the core region and other regions of theenclosure; R3 is a ratio of an area of the core region to an overallarea of the cross section; and R3 is from 0.1 to 0.8.
 33. The LEDfilament in claim 31, wherein: a cross section perpendicular to alongitudinal axis of the LED filament reveals the middle region andother regions of the enclosure; R4 is a ratio of an area of the middleregion to an overall area of the cross section; and R4 is from 0.1 to0.8.
 34. The LED filament in claim 25, wherein the regions of theenclosure are defined by a hypothetical set of parallel planesintersecting the enclosure perpendicularly to a longitudinal axis of theenclosure.
 35. The LED filament in claim 34, wherein: the enclosureincludes two alternating regions including a first region and a secondregion defined by the hypothetical set of parallel planes; the LEDdevice is disposed in the first region; a means for electricallyconnecting the LED devices is disposed in the second region; an outersurface of the enclosure shows a combination of the first region andother regions; R5 is a ratio of a total area of the first region foundon an outer surface of the enclosure to an overall area of the outersurface of the enclosure; and R5 is from 0.2 to 0.8.
 36. An LEDfilament, comprising: an enclosure; a linear array of LED devices; andan electrical connector, wherein the enclosure is a modular structureassembled from modules.
 37. The LED filament in claim 36, wherein theenclosure includes a first module and a second module having a differentset of properties from that of the first module.
 38. The LED filament inclaim 37, wherein the modules of the enclosure are defined by ahypothetical plane perpendicular to a light illuminating direction ofthe linear array of LED devices.
 39. The LED filament in claim 38,wherein: the enclosure includes three modules defined by a pair of thehypothetical planes compartmentalizing the enclosure into an uppermodule, a lower module and a middle module sandwiched by the uppermodule and the lower module; the linear array of LED devices is disposedin the middle module; a cross section perpendicular to a longitudinalaxis of the LED filament reveals the middle module and other modules ofthe enclosure; R6 is a ratio of an area of the middle module to anoverall area of the cross section; and R6 is from 0.2 to 0.8.
 40. TheLED filament in claim 37, wherein the modules of the enclosure aredefined by a hypothetical plane parallel to a light illuminatingdirection of the linear array of LED devices.
 41. The LED filament inclaim 40, wherein: the enclosure includes three modules defined by apair of the hypothetical planes compartmentalizing the enclosure into aright module, a left module and a middle module sandwiched by the rightmodule and the left module; the linear array of LED devices is disposedin the middle module; a cross section perpendicular to a longitudinalaxis of the LED filament reveals the middle module and other modules ofthe enclosure; R7 is a ratio of an area of the middle module to anoverall area of the cross section; and R7 is from 0.2 to 0.8.
 42. TheLED filament in claims 37, wherein the modules of the enclosure aredefined by a hypothetical cylindrical surface having a central axis ofthe LED filament as a central axis of the hypothetical cylindricalsurface.
 43. The LED filament in claim 42, wherein: the enclosureincludes three modules defined by a coaxial pair of the hypotheticalcylindrical surfaces compartmentalizing the enclosure into a coremodule, an outer module and a middle module sandwiched by the coremodule and the outer module; and the linear array of LED devices isdisposed in the core module.
 44. The LED filament in claim 43, wherein:a cross section perpendicular to a longitudinal axis of the LED filamentreveals the core module and other modules of the enclosure; R8 is aratio of an area of the core module to an overall area of the crosssection; and R8 is from 0.1 to 0.8.
 45. The LED filament in claim 43,wherein: a cross section perpendicular to a longitudinal axis of the LEDfilament reveals the middle module and other modules of the enclosure;R9 is a ratio of an area of the middle module to an overall area of thecross section; and R9 is from 0.1 to 0.8.
 46. The LED filament in claim37, wherein the modules of the enclosure are defined by a hypotheticalset of parallel planes intersecting the enclosure perpendicularly to alongitudinal axis of the enclosure.
 47. The LED filament in claim 46,wherein: the enclosure includes two alternating modules including afirst module and a second module defined by the hypothetical set ofparallel planes; the LED device is disposed in the first module; a meansfor electrically connecting the LED devices is disposed in the secondmodule; an outer surface of the enclosure shows a combination of thefirst module and other modules; R10 is a ratio of a total area of thefirst module found on an outer surface of the enclosure to an overallarea of the outer surface of the enclosure; and R10 is from 0.2 to 0.8.48. An LED light bulb, comprising: a base; a light transmissiveenvelope; a stem press; an LED filament; and a plurality of lead wires,wherein: at least part of the base is metal for receiving electricalpower; the light transmissive envelope is mounted on the base; the stempress is mounted on the base within the light transmissive envelope forholding the lead wire and the LED filament in position; the lead wireelectrically couples the base and the LED filament; the LED filamentcomprises an enclosure, a linear array of LED devices and an electricalconnector; the enclosure includes an optically transmissive binder; thelinear of LED devices is conformally wrapped around by the enclosure tobe operable to emit light when energized through the electric connector;and a Cartesian coordinate system having an x-axis, a y-axis and az-axis is oriented for the LED light bulb where: (1) an interfaceconnecting the light transmissive envelope and base falls on the x-yplane; and (2) the z-axis, which is also a longitudinal axis of the LEDlight bulb, intersects the interface at point O.
 49. The LED light bulbin claim 48, wherein: the LED filament defines an arc extendingsubstantially vertically in the light transmissive envelope; an endpointof the arc reaches as high as point H1 on the z-axis; the distance onthe y-axis between the endpoints of the LED filament is D; the length ofthe LED filament on the z-axis is A1; the posture of the LED filament inthe LED light bulb is defined by all points in a set (0, Y, Z+H1), whereZ goes up from 0 to A1 and then from A1 back to 0 as Y goes from −D/2 to0 and then from 0 to D/2; M is a ratio of a length of the LED filamenton the x-axis to a length of the light transmissive envelope on thex-axis; N is a ratio of a length of the LED filament on the y-axis to alength of the light transmissive envelope on the y-axis; P is a ratio ofa length of the LED filament on the z-axis to a length of the lighttransmissive envelope on the z-axis; M is from 0 to 0.05; N is from 0.1to 0.8; and P is from 0.1 to 0.8.
 50. The LED light bulb in claim 48,further comprising a plurality of support wires, wherein: the stem pressincludes a basal portion for attaching the stem press to the base and anelongated post portion for elevating the LED filament to a desiredposition in the light transmissive envelope; the plurality of supportwires radiates horizontally from the post portion to form aspoke-and-hub structure in the light transmissive envelope; the supportwire is attached to the post portion at a first end and to the LEDfilament at a second end; the LED filament defines a sinuous curve alongan arc meandering in the light transmissive envelope; the sinuous curvedefined by the LED filament oscillates in a range from H2+A2 to H2−A2 onthe z-axis, where H2 represents an average height of the LED filamentalong the z-axis in the LED light bulb and A2 represents an amplitude ofthe sinuous curve the LED filament defines; the plurality of supportwires has a same length R; the posture of the LED filament in the LEDlight bulb is defined by all points in a set (X, Y, Z+H2), where−R=<X=<R; −R=<Y=<R; and −A2=<Z=<A2; M is a ratio of a length of the LEDfilament on the x-axis to a length of the light transmissive envelope onthe x-axis; N is a ratio of a length of the LED filament on the y-axisto a length of the light transmissive envelope on the y-axis; P is aratio of a length of the LED filament on the z-axis to a length of thelight transmissive envelope on the z-axis; P is from 0.2 to 0.7; M isfrom 0.2 to 0.8; and N is from 0.2 to 0.8
 51. The LED light bulb inclaim 48, further comprising: an upper LED filament; a lower LEDfilament; an upper set of support wires; and a lower set of supportwires, wherein: the stem press includes a basal portion for attachingthe stem press to the base and an elongated post portion for elevatingthe LED filament to a desired position in the light transmissiveenvelope; the support wire radiates from the post portion to form aspoke-and-hub structure in the light transmissive envelope; the supportwire is attached to the post portion at a first end and to the LEDfilament at a second end; the upper set of support wires is configuredto hold the upper LED filament in position; the lower set of supportwires is configured to hold the lower LED filament in position; theupper LED filament defines an upper sinuous curve oscillating in a rangefrom H4+A4 to H4−A4 on the z-axis, where H4 represents an average heightof the upper LED filament in the LED light bulb and A4 represents anamplitude of the upper sinuous curve the upper LED filament defines; thelower LED filament defines a lower sinuous curve oscillating in a rangefrom H5+A5 to H5−A5 on the z-axis, where H5 represents an average heightof the lower LED filament in the LED light bulb and A5 represents anamplitude of the lower sinuous curve the lower LED filament defines; H5is less than H4; the plurality of support wires have a same length R;the posture of the upper LED filament in the LED light bulb is definedby all points in a set (X, Y, Z+H4), where −R=<X=<R; −R=<Y=<R; and−A4=<Z=<A4; the posture of the lower LED filament in the LED light bulbis defined by all points in a set (X, Y, Z+H5), where −R=<X=<R;−R=<Y=<R; and −A5=<Z=<A5; M is a ratio of an aggregate of lengths of thepair of LED filaments on the x-axis to a length of the lighttransmissive envelope on the x-axis; N is a ratio of an aggregate oflengths of the pair of LED filaments on the y-axis to a length of thelight transmissive envelope on the y-axis; P is a ratio of an aggregateof lengths of the pair of the LED filaments on the z-axis to a length ofthe light transmissive envelope on the z-axis; P is from 0.4 to 1.7; Mis from 0.4 to 1.6; and N is from 0.4 to 1.6.
 52. The LED filament inclaim 31, wherein: the core region has greater thermal conductivity thanthe middle region, the outer region or both by doping in the core regiona greater concentration of particles which are electrical insulatorswhile having greater heat conductivity than phosphor particles; and theouter region has greater thermal radiation power than the middle region,the core region or both by doping in the outer region a greaterconcentration of particles having greater thermal radiation power thanthe optically transmissive binder and greater thermal conductivity thanphosphor particles.